Global Warming: How It Works

 I have a small collection on the bottom shelf of my bookcase of important books.  The books are: How Things Work (4 volumes), Roger Segalat, translated from German; The Way It Works, Robin Kerrod, 1980; The Way Things Work, translated from Italian, 1989; The Way Things Work, David McCauley, 1988; and two massive volumes on the history of science.  That’s what people do – we figure out how things work, and use that knowledge to understand and manipulate the world around us.  

A friend recently asked me, “What is the best argument that a lot of current climate change is caused by humans, through fossil fuel CO2, methane, and other green house gases?  What are the best data and arguments?”   The most important point about climate science is that we know how it works.  It isn’t speculation or correlation.  We simply know how it works.  Since the 1860s or before, people have known that glass bottles filled with CO2 heat up faster than bottles filled with air.  In 1896, the brilliant Swedish chemist Arrhenius calculated how much the earth would warm if CO2 concentration was doubled.  This happened in the same decade that we invented the manual transmission and radio transmission of Morse code, and about a decade after Edison’s electric lightbulb.  Scientific research has continued since Arrhenius, and we know how the CO2 greenhouse effect works just as well as we know how an AM radio, manual transmission, or incandescent lightbulb works.  

We’ve observed and measured the processes that trap heat in the atmosphere and we’ve made predictions of future warming and related events.  To confirm or deny the theory of global warming, scientists set up a system of instrumentation across the planet and in orbit, beginning about 30 years ago.  The data are clear – oceans are warming from the surface downwards, ice is melting in every setting on the planet, and atmospheric temperatures are rising.  We’ve seen the primary predictions of global warming and second-order climate changes robustly confirmed.  Objections and challenges to the data and interpretation have been evaluated and refuted.

How It Works
The entire spectrum of electromagnetic radiation includes gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves and radio waves.  The high-energy end of the spectrum consists of very short wavelengths, including gamma rays and x-rays through visible light, while the low-energy end of the spectrum has longer wavelengths, from infrared through radio waves.  

Everything radiates electro-magnetic radiation at some wavelength.  It’s called by several names –Planck radiation, black-body radiation, or thermal infrared radiation.  The kind of radiation emitted by objects depends on temperature.  Hot objects emit high energy radiation with short wavelengths, and cool objects emit low energy radiation with long wavelengths.  The sun primarily emits energy in the visible spectrum, because it is very hot.  Atmospheric gases are transparent to the visible spectrum, so most of the sun’s energy passes through our atmosphere to reach the ground.  Visible light strikes the earth’s surface and is converted to heat.  The warmed earth also emits radiation, but at a longer wavelength (infrared) because it is cool. The earth’s infrared radiation mostly escapes back into space.  Carbon dioxide, water vapor and methane, however, are partly opaque to infrared radiation, depending on the specific wavelength.  These gases trap heat in the atmosphere, warming the air, the oceans and the ground.  The phenomenon is called the greenhouse effect, because glass will do exactly the same thing, keeping a greenhouse warm – visible light goes in, but infrared radiation is trapped inside.  

Image credit: Science News.  The yellow lines are actual IR readings from space, compared to the theoretical Planck radiation from the ocean surface shown in dark blue.  Depressions and divots in the yellow lines represent absorption of upgoing IR radiation by various greenhouse gases, notably CO2.  Differences between the yellow lines represent clear and cloudy skies, with cloud tops having cooler temperatures and a different baseline Planck profile.

The natural amount of CO2 and water vapor in the air keeps the earth at a temperature to which we’ve  become adapted.  If the earth’s atmosphere had absolutely no CO2 or H2O, the earth’s average temperature would be about 33 C colder, causing freezing conditions over the entire planet.

Of the sun’s incoming radiation (341 W/m2), about 29% (100 W/m2) is directly reflected back into space, mostly by clouds.  The remaining 241 W/m2 is absorbed by the ground and atmosphere, warming the Earth.  The Earth radiates energy back into space at a wavelength in the infrared spectrum, balancing the energy input from the sun to create a stable climate for the past 6000 years.  But the addition of greenhouse gases to the atmosphere is currently trapping 0.94% (3.2 W/m2) of the sun’s energy reaching the surface.  That heat is ultimately redistributed to the oceans, ice, and air, warming the earth.

This figure simplifies many heat transfers within the atmosphere before energy is either retained on earth or returned to space.  The heat retained by greenhouse gases is given the awkward technical term "radiative forcing".

[Technical note: The sun's radiation, measured in space, has an intensity of 1364 W/m2.  There is a range of reported figures from 1361 W/m2 to 1368 W/m2, depending on the choice of instrument calibration.  The earth receives sunlight according to its cross-sectional area, equal to one-quarter of its surface area.  The earth emits radiation from its entire surface area.  So for a simplified energy budget as shown below, we have to choose a convention of adapting numbers for the cross-sectional area or the surface area of the earth.  Most displays adopt the convention of the whole earth surface area as I've done above.  This requires dividing the sun's input radiation by four, yielding 341 W/m2 to represent the average energy input across the entire earth.]

Under natural conditions, a balance develops between the incoming and outgoing radiation, which keeps the earth’s temperature stable, unless disturbed by other factors such as orbital variation.  The earth’s orbit varies over cycles of 40,000 years and 100,000 years, which triggers feedback mechanisms (including CO2 concentration and reflective ice) producing ice ages. 

Climate-change deniers are fond of saying "The climate has always been changing."  But since the last ice age, for the past 6,000 years, the climate has been stable, as proven by geological studies of sea-level, temperature-sensitive isotopes, and ice-sheet deposits.  This is the entire period of the written record of humanity.  The pre-industrial level of CO2 created a “Goldilocks” climate in which humans and nature thrived.

For the past 150 years, we have burned increasing quantities of fossil fuels – coal, oil and natural gas, and cleared or burned forests to create new farmland.

The CO2 emitted from these human activities has markedly changed the concentration of CO2 in the atmosphere, from the pre-industrial level of about 280 parts per million (ppm) of CO2, to the current level of 420 ppm CO2.  Because CO2 is such a potent greenhouse gas, this small change in atmospheric composition has a marked change in retained infrared radiation. 

You might not think that 400 parts per million is enough to change the retention of radiation in the atmosphere.  I’d like to propose a small thought experiment.  Four hundred parts per million is equivalent to four parts in ten thousand, or one part in 2,500.   One ounce of water contains about 600 drops.  Four and 1/6 ounces of water, about a half-cup, contains 2,500 drops.  Imagine, for a moment (or really try) putting one drop of opaque India ink or dark food coloring into a half-cup of water.  The ink noticeably reduces the visible light transmitted through the otherwise transparent water.  It’s the same with CO2 in the atmosphere.  

Climate Feedbacks
There are further processes known as feedback mechanisms affecting the earth’s heat budget.  Feedbacks are processes that are triggered by changes in Earth’s temperature, which either amplify (positive) or diminish (negative) the primary changes.  The strongest feedback effect is the Planck effect, a negative feedback.  As the Earth’s temperature rises, it radiates energy more strongly, counteracting the influence of greenhouse gases.  The balance between the sun’s incoming energy and the Planck effect is what caused the Earth to settle at a stable temperature.  The second strongest feedback is water vapor.  As the ocean surface becomes warmer, the equilibrium humidity in the air rises.  Also, warmer air can hold more humidity, keeping additional water vapor in the air.  Higher humidity is a positive feedback mechanism, because water vapor is itself a powerful greenhouse gas.  So as the planet warms, more heat is retained by water vapor.  As Arctic snow and ice melt, the surface reflectivity diminishes, causing positive feedback.  Climate change increases cloudiness, causing feedback effects.  Clouds are complex as a feedback mechanism, with both positive and negative impacts.  Depending on the type of cloud, the primary impact may be to reflect sunlight, or may be to retain infrared emissions from earth.  Overall, clouds are considered to be a positive feedback.  There are more complex feedbacks involving biochemistry and methane, and fast versus slow feedbacks, but these are generally an order of magnitude less significant than the physical feedbacks.  This is an area of active climate research.

The Planck effect dominates all other feedback mechanisms, and the total impact of all feedback effects is negative.  This is very good, because a simple modeling exercise shows that the global climate would soon irreversibly blow up if the total feedback were positive.  Nevertheless, there are number of authoritative sources on climate feedbacks (notably Wikipedia and Andrew Dessler’s Modern Climate Change) that neglect to mention the Planck effect among climate feedbacks and assert that the net climate feedback is positive.  This is incorrect.

Global temperature change since pre-industrial times is about 1.1 C, so the current total feedback is -1.3 W/m2.  Combining the greenhouse gas effect with total feedback leaves a positive (warming) climate influence of 1.9 W/m2.  

Validation
Climate science predicts that the earth should be warming, due to heating resulting from the buildup of greenhouse gases.  These greenhouse gases, particularly CO2, are unquestionably from human activities (see my blog post, https://dougrobbins.blogspot.com/2019/12/understanding-source-of-rising.html).  We have detailed temperature records for much of the world for the past 150 year or so, and we have plentiful temperature measurements of the oceans beginning in about 1950.  However, early climate data have a few issues with data quality and coverage.

Starting around 1990, scientists put in place a comprehensive set of instrumentation specifically designed to detect and measure global warming.  These systems have corrected some of the issues of data collection from early research, and provide unprecedented coverage of our planet.  The results are unequivocal.  The oceans are warming from the surface downwards; the air is warming over the oceans; the air is warming more rapidly over land; the Arctic is warming faster than the rest of the planet; and continental glaciers, Arctic sea ice, and the Greenland and Antarctic ice caps are melting.  Other, second order effects of the heat are well-proven also, including an acceleration of rising sea level and seasonal changes in physical and biological systems.

There is simply no point to denying that global warming and resulting climate changes are happening due to human emissions of greenhouse gases.  These changes are observed to be accelerating, as expected, due to higher concentrations of greenhouse gases.  Previous predictions about climate change have been highly accurate.  There is no reason to doubt further predictions of serious to catastrophic harm from future climate change unless we greatly curtail emissions of greenhouse gases.

Appendices
Appendix 1
Climate change indicators and sources
Air Temperature Over Land and Oceans
https://data.giss.nasa.gov/gistemp/graphs_v4/

Temperature Anomaly Map, 2016-2022 vs. 1951-1980
Note Arctic warming is more intense than the rest of the planet, as predicted by the Macdonald report in 1979.  Also note that air over land is warming faster than air over oceans.
https://data.giss.nasa.gov/gistemp/maps/

Ocean Heat Content and Temperature
Note that the ocean is warming from the surface downwards.
https://www.ncei.noaa.gov/access/global-ocean-heat-content/index3.html
https://www.ncei.noaa.gov/access/global-ocean-heat-content/index.html

Continental Glaciers, World Glacier Monitoring Service
https://wgms.ch/global-glacier-state/

Arctic Sea Ice Extent (July)
http://nsidc.org/arcticseaicenews/

Antarctic and Greenland Ice Sheets
https://climate.nasa.gov/vital-signs/ice-sheets/

Sea Level Rise
https://climate.nasa.gov/vital-signs/sea-level/

Appendix 2, Comparison of Descriptions of Greenhouse Gas Heating
Arrhenius, 1896
“The selective absorption of the atmosphere is…of a wholly different kind [than diffusion of ultraviolet radiation]. It is not exerted by the chief mass of the air, but in a high degree by aqueous vapour and carbonic acid [CO2], which are present in the air in small quantities.  Further, this absorption is not continuous over the whole spectrum, but nearly insensible in the light part of it, and chiefly limited to the long-waved part, where it manifests itself in very well-defined absorption-bands, which fall off rapidly on both sides.  The influence of this absorption is comparatively small on the heat from the sun, but must be of great importance in the transmission of rays [thermal infrared, or long-wave radiation] from the earth.” 
Arrhenius then describes the debate over whether water vapor or CO2 has the greater influence as a greenhouse gas. 

Asimov, 1959
"The light rays of the Sun hit the air, pass through a hundred miles of it, hit the surface of the Earth, and are absorbed. The Earth heats up.  The heated Earth radiates energy at night back into space, in the form of the far less energetic infra-red.  This also passes through the atmosphere.  The warmer Earth grows, the more heat is radiated away at night.  At some particular equilibrium temperature, the net loss of radiation by Earth at night equals that gained by day so that, once the temperature (whatever it is) is reached, the Earth as a whole neither warms nor cools with time.
Carbon dioxide, however, introduces a complication.  It lets light rays through as easily as do oxygen and nitrogen, but it absorbs infra-red rather strongly.  This means that Earth’s nighttime radiation finds the atmosphere partially opaque, and some doesn’t get through.  The result is that the equilibrium temperature must rise a few degrees to reach the point where enough infra-red is forced out into space to balance the Solar input.  The Earth is warmer (on the whole) than it would be if there were no carbon dioxide at all in the atmosphere.  The warming effect of carbon dioxide is called the “greenhouse effect”.
…A recent set of calculations indicate that if the present carbon dioxide level should double, the overall temperature of the Earth would rise by 3.6 C."
Asimov was reporting on the work of G.N. Plass, published in 1958. 

Ramaswamy, 2019
“Interactions of the incoming solar radiation and outgoing longwave radiation with Earth’s surface and atmosphere affect the planetary heat balance and therefore impact the climate system.”

Also see:
Ramaswamy, Radiative Forcing of Climate Change, 2001

Ramaswamy, Radiative Forcing of Climate: The Historical Evolution of the Radiative Forcing Concept, the Forcing Agents and their Quantification, and Applications, 2019

R. J. Bantges & H. E. Brindley, On the Detection of Robust Multidecadal Changes in Earth’s Outgoing Longwave Radiation Spectrum, 2016

A. Dessler, Modern Climate Change, Third Edition, 2022

IPCC Reports, Technical Summaries, various dates.

Appendix 3, Discussion of Climate Feedback Discrepencies
Wikipedia asserts that there is a net positive feedback to warming.  However, a check of the referenced IPCC Technical Summary for AR5 (2014) is less clear and does not explicitly mention Planck radiation, the strongest negative feedback.  Andrew Dessler’s Modern Climate Change also concludes that total feedbacks are positive.  Dessler also does not mention Plack radiation as a feedback parameter.  [Dessler quantifies the total feedback relative to radiative forcing, rather than temperature change, which makes direct comparison of the feedback numbers a little more difficult.]  On the other hand, Global Climate Models, by D.L. Hartman, clearly identifies each feedback component, including Planck radiation.  Hartman states “the best estimate of the total feedback is about −1.2 ± 0.6 W m−2 K−1, but it is uncertain by about ±50%.”   The IPCC AR6 preliminary Technical Summary also concludes that total physical feedbacks are negative, with a best value of about -1.2 ± 0.7 W m−2 K−1.  I think that the value of -1.2 W m−2 K−1 is likely to be the best estimate.

References:
Svante Arrhenius, On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground, 1896.
https://www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf

Isaac Asimov, "No More Ice Ages?", 1959
In Fact and Fancy, 1972

Ocean heat content, NOAA
https://www.ncei.noaa.gov/access/global-ocean-heat-content/ 

ARGO Ocean Temperature Program Homepage
https://argo.ucsd.edu/ 

NOAA Annual Greenhouse Gas Index
https://gml.noaa.gov/aggi/aggi.html 

Lambeck et al, Sea level and global ice volumes from the Last Glacial Maximum to the Holocene, 2014
https://www.pnas.org/doi/10.1073/pnas.1411762111

Doug Robbins, atmospheric CO2 and related charts, 2022.
http://dougrobbins.blogspot.com/2022/04/charts-of-atmospheric-co2-carbon.html 

NASA GISS Annual Mean Temperature over Land and over Oceans
https://data.giss.nasa.gov/gistemp/graphs_v3/

G. Macdonald, JASONs presidential science advisory report, excerpt, 1979.
https://climatestate.com/2019/07/10/the-jason-report-the-long-term-impact-of-carbon-dioxide-on-climate-1979/
Whole report:
https://irp.fas.org/agency/dod/jason/co2.pdf 

Dennis Hartmann, Global Climate Models, 2016 (feedback chart)
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/climate-feedback
IPCC AR6 Technical Summary (feedback chart, pg. 96)
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf

Andrew Dessler, Introduction to Modern Climate Change, Third Edition, 2022

Is Something Really Safe Because It Is Natural?

 A few years ago, a good friend, Alison Warn, posted a brilliant, concise FB comment about the safety and hazards from artificial and natural sources.  Here's Alison:

"Ahem: Ricin, Oleander, Hydrochloric Acid, Formaldehyde, Tuberculosis, Taipei Venom, Curare, Cyanide, Staphylococcus Aureus, Ebola, Arsenic, Methylmercury, Lead, Lionfish, Radon Gas, Saltwater Crocodiles.... need I go on?

Safety has nothing to do with source and everything to do with inherent properties such as chemical structure, radiation, germ virulence, or teeth. Some synthetic materials are indeed quite dangerous (sarin gas, anyone?) while others are harmless. Some natural materials are indeed quite harmless, while nature has also given us many of our most deadly poisons.

Being blinded by the source can be quite dangerous - it both leads us away from potentially lifesaving synthetic materials (such as promising new pharmaceuticals) and can lead to our discounting some very dangerous natural threats."

---

Whether something is safe or not has nothing to do with whether it is "natural" or not, and everything to do with its physical and chemical properties.  And something artificial is not necessarily any riskier than a natural substance.

Charts of Atmospheric CO2, Carbon Isotopes, Oxygen and Methane

 I started making charts of atmospheric CO2 in 2009, when the global average CO2 concentration was 386 ppm.  I updated my charts in 2012, at 392 ppm, and in 2017, at 405 ppm, and at the end of 2021, at 418 ppm. 

The monitoring stations are located from the far north, at 82° N in Canada to the South Pole.  Scripps Institute has managed most of these stations since the 1950s, first under the direction of Charles Keeling, and later under his son, Ralph Keeling.  I also included records from a few obsolete legacy stations that were operated by foreign governments.  I standardized my chart displays using cool colors to represent the Northern Hemisphere, and warm colors for the Southern Hemisphere.

The amplitude of the CO2 seasonal cycle varies with latitude, from high amplitude in far northern latitudes to very little amplitude at the South Pole.  The seasonal cycle is driven by seasonal plant growth and decay on lands with temperate climate, which are concentrated in the Northern Hemisphere.  Agriculture, which is also concentrated in the Northern Hemisphere, also contributes to the seasonal cycle.  I took advantage of this for my standard display, overlaying low amplitude over higher amplitude traces, so that all traces can be seen.

In general, CO2 concentration in the atmosphere is growing exponentially, a fact noted by Isaac Asimov in 1959.  In 2009, I made an exponential function, beginning at the pre-industrial CO2 concentration of 280 ppm in 1800, with an eyeball-fit to the data from 1957 to 2009.  Here’s the function, and the chart beginning in 1800, updated with CO2 data through 2021.  This chart has the “hockey stick” impression that characterizes many climate-change charts.

CO₂ concentration, ppm = e^(n*0.001854) + 280, where n = the number of months since Jan. 1800

This function would predict that global CO2 would pass 450 ppm in January, 2032 (ten years from now), and pass 500 ppm in August, 2043.

The exponential function seems to be slightly overstating the rate of CO2 growth since 2009, so I tried an alternate formula for the forecast in coming decades, a second-degree polynomial with a least-squares fit to the global average CO2 from 1974 to 2009.  That formula is CO2 in ppm = 0.000104*x²+0.0897*x+331.66, where x is the number of months from July, 1974.  This formula predicts global CO2 will pass 450 ppm in June, 2034, and pass 500 ppm in July, 2050. 

Certainly, these forecasts are simple extrapolations, and include none of the analysis of policies and economics which should be the basis of forecasting.  But it’s worth noting that my exponential forecast from 13 years ago is pretty much right on the money, overshooting by only one or two parts per million.  The last thirteen years has seen unprecedented growth in renewable energy technologies, but so far without significant impact on the rate of CO2 growth.  Here are the two forecasts on the same chart.

The seasonal cycle can easily be filtered from the data, leaving the long-term trend at each station.  From this, it’s easy to see that the Northern Hemisphere leads the Southern Hemisphere in rising CO2.  About 90% of fossil fuel burning happens in the Northern Hemisphere, and CO2 accumulates in the far north, while dispersing to the south. 

The difference in concentration from the far north to the South Pole has been increasing as larger volumes of fossil fuels are burned each year, from about 3 ppm in the 1980s to over 5 ppm now.  The chart below shows the difference in the one-year time-averaged CO2 concentration measured in Alert, Canada, at latitude 82° North, and the South Pole. 

The amplitude of the seasonal cycle has also been increasing in the far north.  The amplitude of the cycle increased from 15 ppm to 20 ppm since the mid-1970s.  This probably reflects increased agriculture and farm productivity in the Northern Hemisphere as world population has doubled.  Previous work showed that seasonal fossil-fuel use is volumetrically inadequate to produce the change in the atmospheric CO2 seasonal cycle.  https://dougrobbins.blogspot.com/2012/04/modeling-global-co2-cycles.html

Carbon comes in two common naturally occurring isotopes, C¹² and C¹³.  Various processes, including life processes, sort the isotopes, favoring the accumulation of one or the other isotope.  Photosynthesis favors C¹², so everything with carbon derived from plants, including lumber, your mashed potatoes, you, me, and fossil fuels is enriched in C¹².  Scientists use a measure of the C¹³/C¹² ratio written as d¹³C , and called delC13.  As fossil fuels are burned the C¹²-enriched carbon in CO2 changes the ratio of these isotopes in the atmosphere, lowering the value of delC13.  DelC13 continued to fall from 2009 to 2021, reflecting a growing fraction of carbon from fossil fuels in the atmosphere. 

Carbon isotopes in the atmosphere are also affected by the seasonal cycle of plant growth on the temperate land mass of the Northern Hemisphere.  As plants grow during the northern summer, the lighter isotope C¹² is preferentially removed from the atmosphere, and returned during the winter months as plants decay.

After filtering the seasonal cycle, we see that the Northern Hemisphere leads the Southern Hemisphere in falling DelC13.  As an aside, the residual fluctuations in the trend have a strong correlation to the Oceanic Nino Index (ONI), reflecting sea surface temperatures in the Pacific.  https://dougrobbins.blogspot.com/2013/11/carbon-isotopes-in-atmosphere-part-ii.html

Interestingly, if all of the carbon released by fossil fuels stayed in the air, the DelC13 value would be much lower, about -13, instead of -8.5.  The measured dilution of carbon with the isotope signature of fossil fuels provides a way of estimating the volume of all carbon reservoirs exchanging carbon with the atmosphere.  Currently, the reservoirs freely exchanging carbon with the atmosphere have a carbon mass of about 5200 gigatonnes, before accounting for additional carbon in the system from new burning of fossil fuels.  That’s about 6 times the mass of carbon currently in the atmosphere.  https://dougrobbins.blogspot.com/2013/11/how-big-is-carbonsphere.html

Atmospheric oxygen is also influenced by burning of fossil fuels.  Oxygen is consumed, causing atmospheric O2 to fall.  The atmosphere is about 21% oxygen, and the decline is only about 0.08%, so there is no threat to breathing.  Still, the decline can be measured precisely.  The decline in oxygen is reported in units per meg, which is equivalent to ppm in this range of values.

After filtering the seasonal cycle, we see that the Northern Hemisphere leads the Southern Hemisphere in oxygen decline, because most fossil fuels are burned in the Northern Hemisphere.  The total volume of oxygen decline is very close to the expected consumption of oxygen considering the reported volumes of fossil fuels burned and deforestation, as reported in this previous post.  https://dougrobbins.blogspot.com/2019/12/understanding-source-of-rising.html

Atmospheric methane (C4) is also increasing as a result of human emissions.  Methane is a much more powerful greenhouse gas than CO2, but has a shorter lifespan.  CO2 has a half-life of 120 years, while methane has a half-life of about 10 years.  This is why the climate scientists use the parameter GWP (global warming potential) to represent the different strength of various greenhouse gases over an effective time frame.  The GWP of CO2 equals 1, by definition, for all time intervals.  For methane, the warming potential over 20 years (GWP-20) is 84 – 87, and over 100 years is 28 – 36.  Over shorter intervals, methane is an even stronger greenhouse gas.  Currently, methane concentration in the atmosphere is about 1.9 ppm (i.e. 1900 ppb).  In absolute terms, methane warmed the earth by about 0.52 W/m2, compared to 2.11 W/m2 for CO2, for the latest year reported by NOAA, 2020.  All other greenhouse gases combined contributed another 0.55 W/m2.  Methane also has a seasonal cycle in both hemispheres with high values in the summer and low values in the winter, but I don’t know the explanation for the seasonal cycle. 

As the concentrations of CO2 and methane in the air rise, the atmosphere will absorb heat at a faster rate, leading to destructive climate change.  Temperatures and climate change will not stabilize until carbon emissions reach zero.  I will update my charts on carbon emissions when summary data for 2021 is released in the BP Statistical Summary of World Energy in July.  Apart from a small pandemic-related decline in emissions in 2020, the world continues to add CO2 to the atmosphere at an ever-increasing rate.  If the world had acted to reduce emissions three decades ago, simply reducing emissions might have been a reasonable policy.  However, in our current situation, outright elimination of carbon emissions is required to avoid some level of catastrophic consequences. 

Globally, we need to reduce emissions to 50% by 2035, and to zero some time between 2050 and 2070.  I am very pessimistic that we have the public understanding or political will to reach these goals.  As Bill Gates wrote in 2021, "To avoid a climate disaster, we have to get to zero greenhouse gas emissions….The case for zero was, and is, rock solid.  Setting a goal to only reduce our emissions—but not eliminate them—won’t do it.  The only sensible goal is zero.”

References:

CO2, CO2 carbon isotopes, oxygen and methane data, including obsolete CO2 stations

https://scrippsco2.ucsd.edu/data/atmospheric_co2/sampling_stations.html

https://scrippso2.ucsd.edu/data.html

https://gml.noaa.gov/dv/data/

https://data.ess-dive.lbl.gov/view/doi:10.3334/CDIAC/ATG.015

https://www.osti.gov/dataexplorer/biblio/dataset/1409297

https://carbonmapper.org/data/

Isaac Asimov, "No More Ice Ages?" prediction and commentary on global warming,
in Fantasy and Science Fiction, Jan. 1959, republished in Fact & Fancy, 1962 and Asimov on Chemistry, 1974. 

Global Warming Potential

https://www.epa.gov/ghgemissions/understanding-global-warming-potentials#:~:text=Methane%20(CH4)%20is%20estimated,uses%20a%20different%20value.).

GWP-20 for methane = 84 to 87; GWP-100 for methane = 28 to 36 (also reported as 25)

Radiative Forcing for various greenhouse gases

https://gml.noaa.gov/aggi/aggi.html

George Will: Willful Ignorance About Climate Change

 

The Washington Post recently published an op-ed on climate change by aging political commentator George Will.  (August 12, 2021, https://www.washingtonpost.com/opinions/2021/08/11/with-closer-look-certainty-about-existential-climate-threat-melts-away/, too bad about the paywall).  Will’s commentary appears to be drawn exclusively from a book by noted climate-change denier Steven Koonin.  George Will has been a climate-change denier since at least 2007, holding forth on a variety of ideas which were either false at the time or have been subsequently debunked. 

There are very basic errors of fact throughout Will’s current column.   His talking points seem to drawn from the early 1990s, and he is oblivious to the quantity of definitive data about the climate that has been gathered over the past 30 years.

Will begins by saying, “There is a low ratio of evidence to passion in today’s exhortations to combat climate change.”  Ridiculous.  Climate change is probably the most intensively studied scientific topic in history, with tens of thousands of scientific reports written by thousands of scientists.  Over the last three decades, scientists have implemented monitoring systems specifically designed to measure the impact of greenhouse gases on the global climate.  We are closely measuring incoming energy from the sun; energy radiating from the earth into space according to wavelength, measuring the impact of greenhouse gases; the temperature and heat content of the oceans to 2000 meters, the temperature of the air from the surface to the stratosphere, the mass of the ice caps, the area, thickness and age of Arctic sea ice, the melting of continental glaciers; the temperature of the ocean surface; global changes in sea level; the CO2 and methane content and isotope chemistry of the atmosphere, etc.  Considering all of these data, the IPCC 6th Assessment Report reaches a clear conclusion: that warming of the global climate due to human activities is an unequivocal, established fact.

The early draft of Volume I of the IPCC 6^th Climate Appraisal runs over 3500 pages, written by about 300 authors.  The full report, when completed, will involve about 700 authors.  The US Fourth National Climate Assessment weighs in at over 1500 pages by 300 scientists from 13 US government agencies.  These follow on three decades of earlier reports with contributions from thousands of scientists, representing tens of thousands of scientific papers.  There is not a lack of evidence regarding climate change.

Will repeats the hoary comment that the climate is always changing, which is completely irrelevant.  The point is that the climate is rapidly changing now due to human emissions of greenhouse gases, and we know it.  This self-induced fiasco will cause substantial harm to people and nature in coming decades, and has already begun.  Past changes have no bearing on our problem. 

Will complains that science has limited ability to disentangle human and natural influences in the climate changes during the Little Ice Age (1450 – 1850), or in the cooling period from 1940 – 1980.  Will is misconstruing lack of data for a lack of understanding.  Using Will’s reasoning, if a doctor is unable to diagnose the cause of death for King Francis II of France (1544 – 1560), why would anyone go to a doctor today?  The answer is obvious; it is because the doctor looking at today’s patient has MRI images, blood chemistry, and a host of other diagnostic medical tools.  Similarly, the instrumentation for earth systems implemented in the past 30 years allows us to clearly diagnose what is happening to the climate now.

Will states that sea level has been rising a few millimeters a year for 20,000 years, and cites a source which denies that sea level has been rising over the past century, or that melting of ice-sheets is currently higher than in the past.  These points are patently false.  Sea level rose sharply at the end of the last ice age about 20,000 years ago, but stabilized about 5000 years ago.  In the past 5000 years, sea level has risen only about a meter, rising at a rate of about 0.2 mm/yr to the present (Lambeck et al, 2014; also R. Rohde, Berkeley Earth, from other published data).  Sea level is a proxy for climate, and stable sea level implies a stable climate in the last five millennia.  According to satellite measurements, the current rate of sea level rise is now 15 times faster than the past 5000 years, and accelerating. Continuous coastal sea-level measurements dating from the 1800s also verify the acceleration of sea-level rise.  Melting ice accounts for about 60% of that rise, with thermal expansion of the warming ocean accounting for the rest.  Will’s point in the same paragraph, about relatively little change in the average warmest temperature in the United States is cherry-picking the various parameters (change in lowest temperature, change in average temperature, change in winter temperatures, etc.) to find the parameter with the least change, in a deliberate attempt at obfuscation and distortion.

Sea level stabilized about 6000 years ago, meaning that climate also stabilized after deglaciation following last ice age. 

Will disputes media reports that hurricanes are increasing in number and intensity.  The concern about hurricanes is not about what has happened thus far, but what will happen as climate change advances.  The sea surface temperature is rising.  Hurricane strength and frequency are driven by higher sea surface temperatures and will inexorable become stronger and more frequent in the future.  Scientists are not correlating hurricane strength to greenhouse gases and making an extrapolation; scientists are forecasting stronger hurricanes because they understand how things work.

Hurricane wind speed versus sea surface temperature, modified from Robert Rohde, Berkeley Earth.  Higher sea surface temperatures will inevitably mean stronger hurricanes.  Sea surface temperatures are inexorably rising.

Will attempts to deflect responsibility for rising CO2 from the developed world to the developing world, citing plans to increase fossil-fuel power production in India and China.  In this, Will is neglecting the 150-year history of fossil-fuel use by industrialized countries, which have brought us to the brink of climate disaster, where we stand today. 

Will concludes by referencing a “previous UN report” (not cited) which projects minimal economic harm from climate change.  There is no indication of when this report was written, or my whom.  But that report does not reflect the views of the climatologists of the IPCC, or US scientists who wrote the 4^th National Climate Assessment.  The IPCC 1.5 Special Report states: “Climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5°C and increase further with 2°C.” (Summary for Policy Makers, section B.5.)  Likewise, the United States’ Fourth Climate Assessment (2018) states: “Climate change creates new risks and exacerbates existing vulnerabilities in communities across the United States, presenting growing challenges to human health and safety, quality of life, and the rate of economic growth….Without substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses to American infrastructure and property and impede the rate of economic growth over this century.” 

George Will is misguided and uninformed about climate change.  Will has read one discredited book by one discredited scientist, who is not a climatologist, instead of the well-documented publications from respected institutions of science.  Will’s column is part of the general celebration of ignorance and lies which characterize the Conservative movement, on issues from the treatment of COVID-19 to the 2020 election loss by Donald Trump.  George Will’s column on climate change is a classic example of Willful Ignorance. 

References
https://www.washingtonpost.com/opinions/2021/08/11/with-closer-look-certainty-about-existential-climate-threat-melts-away/

George Will’s recent column.

https://www.desmog.com/george-will/
Will’s former statements about climate change.

https://www.ipcc.ch/sr15/
IPCC Special Report on Global Warming of 1.5 degrees C.
https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/
IPCC Sixth Assessment Report, Volume I, The Physical Science Basis, 2021.

Fourth National Climate Assessment Volume I, Physical Science 2017.
https://nca2018.globalchange.gov/
Fourth National Climate Assessment, Volume II: Impacts, Risks, and Adaptation in the United States, 2018.

https://www.pnas.org/content/111/43/15296

Lambeck et al, Sea level and global ice volumes from the Last Glacial Maximum to the Holocene, 2014.

https://commons.wikimedia.org/wiki/File:Post-Glacial_Sea_Level.png
Robert Rohde, Berkeley Earth, Holocene Sea-Level Chart, 2005.
https://twitter.com/RARohde/status/907918199202701344/photo/1
Robert Rohde, Berkeley Earth, Tropical Storm Wind Speed Versus Water Temperature, 2017.

Global Warming, Natural Cycles and Unicorn Farts

 "The suggestion that natural causes are contributing to global warming is entirely speculative.  If someone proposes that natural causes are warming the earth, they need to identify, observe and quantify the specific process that is occurring.  It may be true that unicorn farts, rather than greenhouse gases, are warming the earth over the past century.  But the burden of proof is on the unicorn advocates.  They need to find the unicorns, observe and measure the heat generated per unicorn fart.  They need to demonstrate that unicorn farts are sufficient to account for a significant portion of global warming, and to either discredit the physics of greenhouse gases or to identify a previously undetected heat sink on the scale of the global ocean to account for the displacement of greenhouse gas heat.  They also need to demonstrate that unicorn farts are delivering heat to the surface of the ocean and cooling the stratosphere.  The notion that “we just don’t know what is warming the earth” is not a viable statement.

I recently had a call with a staffer for Alaska’s more conservative U.S. Senator.   I had made a trip to DC, and Alaska’s Congressional Delegation will usually make time to meet with constituents who travel 3350 miles from home.   I had sent meeting requests to both Senators, and the moderate Senator’s staff contacted me, and we had a good discussion of climate change.  The more conservative Senator’s office contacted me after I sent a complaint comparing their non-responsiveness to the moderate Senator.  In my call with the staffer, I discussed the points on my agenda:

1) That we needed to cut CO2 emissions 50% by the year 2035 and to zero by 2050, to avoid a climate disaster. 

2)  Achieving those cuts will be very difficult and costly.  Real climate solutions need to be affordable, scalable, timely, environmentally acceptable, and technologically mature.  There are no currently viable solutions, as global upscaling of renewable energy runs into problems with increasing costs and timeliness. 

3)  We cannot count on negative emissions technologies to provide a climate solution due to similar issues with global scaling of these technologies. 

4)  Historically, the United States disproportionally contributed to the climate crisis, and we will be held responsible, accountable, and liable for damages to other nations in the future. 

5)  Because we are disproportionally to blame, we are morally obligated to lead the world in reducing emissions. 

6)  In the case of south-central Alaska, replacing our fossil-fuel electrical generation will require about 1000 new wind turbines, plus short-term and seasonal energy storage.  Powering a full fleet of electric vehicles will require at least another 1000 wind turbines, and replacing space heating by fossil fuels will require at least another 1000 wind turbines, all to be accomplished by 2050.  For reference, building an 11-turbine wind farm near Anchorage required a decade of planning and two years of construction.

7) A carbon tax is the best way to meet emission reduction goals, starting small, and increasing until renewable energy or carbon sequestration is commercially justified.

The staffer listened politely to my sermon, at points offering small interjections.  He commented that the Senator sponsored legislation to reduce the permitting obstacles to building more wind turbines.  I responded that it was a nice ideological gesture, but the real problem in building more wind energy wasn’t permitting, it was the availability of capital.  The great majority of cost for fossil-fuel generation is in fuel expense, which is spread out across the life of the power plant.  The great majority of cost for renewable energy is in capital, which must be funded up-front.  The staffer added that it was an exciting time for renewable energy; and that there was much interest and activity in Congress for doing more.

At the end of our conversation, I took issue with one of the Senator’s canned response letters regarding climate change.  The Senator’s previous position was that we don’t know how much of climate change is due to human greenhouse gas emissions, and how much is due to natural factors.  I said that was false.  “It is?” questioned the staffer, sounding surprised.  “Yes”, I replied.  “That’s complete bullshit.  All of climate change is due to human influences; one hundred percent.  There are no natural processes or cycles that are adding heat to the earth to the degree and over the time frame that we have observed global warming.”  Shortly afterward, we concluded the call. 

In retrospect, I wasted a good opportunity to provide a real explanation to someone who could make a difference in forming policy.  In the fashion of introverts everywhere, here is what I should have said. 

Global warming is by now a well-quantified problem.  The physics of greenhouse gases has been understood for 125 years.  The physics of global warming has been well-quantified since the 1980s, when satellites began measuring incoming solar radiation, and outgoing radiation was measured at the surface, and at various altitudes up to the stratosphere, and later by satellites.  What was happening to that heat was still somewhat uncertain in the 1990s, but in the early 2000s instrumentation was devised to measure the temperature of the ocean to a depth of 2000 meters, and to monitor the mass of the polar ice caps, Arctic sea ice, and continental glaciers.  The system of measuring surface temperatures was also improved with the addition of satellite observations.  Considering all of this information, we now have twenty years of comprehensive measurements for the earth’s heat budget. 

The first point is that heat from greenhouse gases is fully sufficient to account for the heat now appearing in earth’s heat sinks, with an imbalance of only a few percent.   If a natural source of heating existed, it would raise another problem – what is happening to the heat from greenhouse gases?  In order to validate a natural source of heat, either the physics of greenhouse gases needs to be overturned (which isn’t going to happen), or we have somehow overlooked a heat sink on the scale of the global ocean.  This also is extremely unlikely. 

A second point is that any alternative explanation of global warming must also explain the pattern of heat flow.  Observations show that the oceans, which absorb more than 90% of the heat from greenhouse gases, are warming from the surface downwards.  This implies heating at the surface, either from increased solar radiation or by conduction from the atmosphere.  We have forty years of satellite observations of the solar radiation, conclusively proving that the solar radiation is declining slightly, not increasing.  Any speculative natural process for global warming must necessarily deliver heat to the surface of the ocean, from the atmosphere.  This rules out any speculative heat source involving ocean currents or cycles.

A final point is that there are no known natural systems adding new heat to the earth over the past five decades.  Geologists, oceanographers, and meteorologists have done a pretty good job over the past 200 years, identifying the processes operating on the earth's surface.  No process that would add new heat to the planet's surface, over the time that global warming has occurred, has been identified.  Natural systems do have some cyclicity that affect the global climate.  Ocean cycles generally operate over periods of a decade or less, not over the multi-decade time scale that we observe heat appearing in earth systems.  But one important thing to note is that these natural cycles are zero-sum; they redistribute heat but don’t add new heat to the earth.  As noted above, solar radiation varies according to the eleven-year solar cycle, but there is no continuing warming persisting beyond those cycles. 

The argument that natural causes are contributing to climate change is entirely speculative.  If someone is proposing that natural causes are warming the earth, they need to identify, observe and quantify the specific process that is occurring.  It may be true that unicorn farts are warming the earth, rather than greenhouse gases.  But the burden of proof is on the unicorn advocates, to find the unicorns, observe and measure the heat generated per unicorn fart.  They need to demonstrate that unicorn farts are sufficient to account for a significant portion of global warming, and to either discredit the physics of greenhouse gases or to identify a previously undetected heat sink on the scale of the global ocean, to account for the displacement of greenhouse gas heat.  They also need to demonstrate that unicorn farts are delivering heat to the surface of the ocean, and cooling the stratosphere. 

The notion that “we just don’t know what is warming the earth” is not a viable statement. 

References

Written testimony of climatologist Zeke Hausfather to the US House Committee on Space, Science and Technology, , p. 13, 3/12/2021  https://science.house.gov/imo/media/doc/Hausfather%20Testimony.pdf

“Our best estimate is that approximately all of the observed global mean surface temperature warming since the 1950s is due to human emissions of CO2 and other greenhouse gases. Natural climate “forcings” such as changing solar output, variations in the Earth’s orbit, and volcanic activity would have likely led to a slight cooling over the past 70 years in the absence of human influences on the climate.”  

IPCC 6^th Assessment Report, Headline Statements from the Summary for Policymakers, 8/9/2021 (draft)  https://www.ipcc.ch/report/ar6/wg1/#SPM

“A.1 It is unequivocal that human influence has warmed the atmosphere, ocean and land.” – Policy-makers’ Headline Statements, first line. 

“Human influence on the climate system is now an established fact:…It is unequivocal that the increase of CO2, methane (CH4) and nitrous oxide (N2O) in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere and biosphere.” Pg. TS-8

“Table TS.1:  Synthesis:  Warming of the global climate system since preindustrial times], Observed Change Assessment – Established Fact; Human Contribution Assessment – Established Fact.”  Pg. TS-33.

‘Less than 1% probability’ that Earth’s energy imbalance increase occurred naturally, say Princeton and GFDL scientists, Liz Fuller-Wright, 2021. https://www.princeton.edu/news/2021/07/28/less-1-probability-earths-energy-imbalance-increase-occurred-naturally-say

“[Shiv Priyam Raghuraman] and his co-authors used satellite observations from 2001 to 2020 and found that Earth’s “energy imbalance” is growing….’It is exceptionally unlikely — less than 1% probability — that this trend can be explained by natural variations in the climate system,’ said Raghuraman.”

Anthropogenic forcing and response yield observed positive trend in Earth’s energy imbalance, Reghuraman et al, 2021.   https://www.nature.com/articles/s41467-021-24544-4

2020 Climate Review; Global and Alaska

 Unsurprisingly, the global climate in 2021 continued to warm and to experience climate-related disasters.  Global air temperature tied 2016 as the warmest year on record.  Oceans continued to warm, and marked the warmest year on record.  Oceans absorb about 95% of heating from greenhouse gases, and thus have a more consistent increase in temperature.  

According to Carbon Brief, CO2 emissions in 2020 fell by about 7% compared to 2019, due to economic cut-backs during the Covid-19 epidemic.  Nevertheless, average atmospheric CO2 ended the year at about 413.5 ppm, a rise of about 2.5 ppm over 2019 (ESRL/NOAA).  That rate of increase is not significantly different than the previous decade.  For reference, pre-industrial levels of CO2 were about 280 ppm.

Alaska had a relatively mild 2020 in terms of climate change, cooler than recent years, with temperatures in the range of temperatures of the 1980, but still warmer than earlier decades.  There were fewer climate-related wildfires, and the warm-water "blob" in the Gulf of Alaska did not develop during 2020. Nevertheless, the long-term trajectory of climate change in Alaska is still clear.

 Low soil moisture results in dry plants, which cause wildfires to burn hotter and faster.  Low soil moisture also causes dead undergrowth, which provides fuel-loading to forests, increasing fire danger.

Robert Rohde of Berkeley Earth prepared the chart above.  Annual averages of precipitation and temperature during the California fire season are shown in a color spectrum ranging from cool to warm colors representing 20-year intervals.  The chart shows a slow progression toward warmer temperatures, with the most significant change in the last twenty years.  Note that the ten largest wildfires, and the ten most destructive wildfires all occur in the warmest & driest quadrant of the chart.  The amount of change in the past 40 years is dramatic, and sobering if these trends continue over the next 40 years.

Alaska had a relatively moderate year regarding climate events in 2020.  Nevertheless, the long-term trends remain.  NOAA published a report card indicating that changes in the Arctic are likely to be permanent.

 The chart shows temperature change since 1945.

Arctic temperatures are rising two to three times faster than the rest of the globe, as a consequence of feedback factors from loss of snow and ice.  This effect was predicted in climate models by the Jasons' report in 1979.  Note also that air temperatures over land has warmed more than the oceans. 

Oceans absorb about 95% of heat retained by greenhouse gases.  The absorption of heat, and evaporative cooling, keeps air temperatures over oceans lower than over land.  Therefore, air temperatures over land are increasing faster than the global average, which is inconvenient, because we live on land.

Alaska temperatures clearly show the impact of Arctic amplification.  North Slope temperatures in the fall season have been sharply higher since the mid-1990s, due to early loss of Chukchi Sea ice.

Thunderstorms have become measurably more frequent near Fairbanks since about 1990.  The state's biggest wildfires typically occur near Fairbanks, and are most often caused by lightning.

Alaska's climate continues to change rapidly, and future decades are likely to bring serious, detrimental change.