By: Alan Smith of the 350PDX SE Neighborhood team
When reading climate change articles, I have often felt frustrated with how vague their statements have been, or with the narrowness of their focus. Joe Romm, the author who has written the majority of the articles I’ve read, seems to share this feeling. He wrote, “One of the greatest failings of the climate science community (and the media) is not spelling out as clearly as possible the risks we face on our current emissions path, as well as the plausible worst-case scenario, which includes massive ecosystem collapse.”
I thought others may not have read this kind of information either, so I have put together the key bits and pieces from the articles (to which I’ve provided links below) to share with you. Most of what is written below is copied from these articles. I hope you will find this informative and interesting.
The problem, Romm wrote, is that, “So much of what the public and policymakers think is coming is a combination of: 1) the low end of the expected range of warming and impacts based on aggressive policies to reduce emissions (and no serious carbon-cycle feedbacks), 2) analyses of a few selected impacts, but not an integrated examination of multiple impacts, and 3) disinformation pushed by the anti-science, pro-pollution crowd.”
When I read his July 5th article titled “Stephen Hawking issues dire warning about the threat Trump poses to a livable climate,” I also looked at the articles referenced through links embedded in the article and started finding information that answered some of the questions I’ve had.
1. Runaway greenhouse effect.
Hawking warned a runaway greenhouse effect could be the result of Trump’s decision to pull the USA out of the Paris climate deal. It is a process in which a net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its oceans boil away. Other large-scale climate changes are sometimes loosely called a runaway greenhouse effect, although it is not an appropriate description. Other terms, such as abrupt climate change, or tipping points, should be used when describing such scenarios.
It has been estimated that it would require about 30,000 parts per million (ppm) of atmospheric carbon dioxide (CO2) to cause a runaway greenhouse effect. That is about 10 times more atmospheric CO2 than most experts estimate would be released from burning all available fossil fuels (although such high values could be reached by releasing large amounts of CO2 from the Earth’s vast deposits of limestone and other carbonate rocks), so it is unlikely that human activity will lead to a Venus like planet [where the surface temperature is around 872 degrees Fahrenheit (F)]. However, according to a paper published in Nature Geoscience during 2013, new calculations show that a water vapor–rich atmosphere absorbs more sunlight and lets out less heat than previously thought. These new calculations show a runaway greenhouse effect is possible, and without the cooling effects of certain types of clouds, modern Earth would already be well on its way to broiling like Venus.
Microbes could endure and even flourish on a planet at the brink of runaway, but people would still be steam-cooked whether or not such a hothouse world tipped over into a more Venusian climate. Leaving aside other effects of global warming like rising seas, stronger storms, permanent droughts, plummeting biodiversity, new plagues, the collapse of civilization, and the effects that are still unknown, the problem of heat stress alone would become lethal.
2. Paleoclimate Feedback
The deniers denigrate computer models as tools to predict the future of our climate, but paleoclimate data is considerably more worrisome than the models, mainly because the vast majority of the models largely ignore key amplifying carbon-cycle feedbacks, such as the methane emissions from tundra and sea bed hydrates.
Measurements of 56-million-year-old sedimentary rocks have revealed an event during the mid-Cenozoic era called the Paleocene–Eocene Thermal Maximum (PETM) in which a millennia-scale pulse of greenhouse gases warmed the globe. The PETM pulse seems to have been roughly equivalent to what humans could release through burning all recoverable fossil fuels, and may have warmed the planet in excess of 50 degrees F, but clearly no catastrophic runaway occurred. However we do not know how close the Earth came during that time to a runaway greenhouse effect, and the sun now shines 0.4% brighter than it did then (and will continue to increase in brightness over time), so now such a pulse might trigger a runaway greenhouse effect.
The last time the CO2 concentration was as high as 1000 ppm was 35 million years ago (Ma). Then an increase of CO2 from 300 ppm to 1000 ppm warmed the tropics by 9 to 18 degrees F and the polar regions by 27 to 36 degrees F. The Earth was 29 degrees F warmer than is was at the beginning of the industrial revolution. The data also reveal that the reduction of CO2 from this high level to the lower levels of the recent past took tens of millions of years.
3. Today’s Models
Scientists using computer models are not overestimating climate change and in fact they are underestimating it because they are omitting crucial amplifying feedbacks. Carbon dioxide may have at least twice the effect on global temperatures compared to the impact currently projected by computer models of global climate. Three dozen authors conclude that existing climate models are missing crucial feedbacks that can significantly amplify polar warming. Methane released from the tundra and sea bed hydrates is the most dangerous amplifying feedback in the entire carbon cycle. The permafrost tundra alone contains a staggering 1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere, much of which would be released as methane, and methane is 86 times as potent a heat-trapping gas as CO2 over a 20 year time horizon. A 2006 study found that the effect of amplifying feedbacks in the climate system-where global warming boosts atmospheric CO2 levels will promote warming by an extra 15 percent to 78 percent on a century-scale compared to typical estimates by the U.N.’s Intergovernmental Panel on Climate Change (IPCC). The study notes these results may even be conservative because they ignore other greenhouse gases such as methane, whose levels will likely be boosted as temperatures warm.
Models that don’t include feedbacks predict that a global average warming of 7 degrees F would happen by 2100 if we stay on our current emissions path. In this scenario large parts of the inland United States would warm by 15 degrees F to 18 degrees F. According to a 2009 study by the UK Met Office, models that consider feedbacks predict that if we stay on our current emissions path catastrophic climate change, 13 to 18 degrees F warming over most of U.S. and 27 degrees F in the Arctic, could happen by 2060. They call this the plausible worst case scenario, but it isn’t the worst-case, which is the A1F1 scenario (the 1000 ppm scenario). Rather, the case they refer to is known as “A1B,” which is the 720 ppm scenario. Betts and his team do a better job of incorporating carbon-cycle feedbacks into their modeling than virtually anyone else, but they do not incorporate any feedback from methane emissions from the thawing tundra or melting sea bed hydrates — and that is certainly the most worrisome of all of the carbon-cycle feedbacks.
4. Our Permafrost Is Perforated Like A Postage Stamp
Permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere, according to research results published in the March 5, 2010 edition of the journal Science.
The Earth’s geological record indicates that atmospheric methane concentrations have varied between about 0.3 to 0.4 ppm during cold periods to 0.6 to 0.7 ppm during warm periods. Current methane concentrations in the Arctic average about 1.85 ppm, the highest in 400,000 years. Concentrations above the East Siberian Arctic Shelf are even higher. The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the rest of the entire world’s oceans, about 7 teragrams (7.7 million metric tons) of methane yearly.
The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to 3 to 4 times.
Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.
A major 2005 study found that virtually the entire top 11 feet of permafrost soil around the globe could disappear by the end of this century.
If we somehow stabilize CO2 concentrations in the air at 550 ppm, permafrost would plummet from over 4 million square miles today to 1.5 million. If concentrations hit 690 ppm, permafrost would shrink to just 800,000 square miles. The calculations in the study do not include the feedback effect of the released carbon from the permafrost, which has locked in it 2 times more carbon than the atmosphere (and much of that is in the form of methane).
A 2003 study found that a typical fossil fuel emissions scenario for this century, which would have led to carbon dioxide concentrations in 2100 of about 700 ppm without feedbacks, led instead to concentrations of 980 ppm with feedbacks.
Even ignoring feedbacks, keeping concentrations below 700 ppm would have required the United States and the world to start significantly slowing carbon dioxide emissions from coal, oil, and natural gas by 2015 and to stop the growth almost entirely after 2025.
An April 2017 study found global warming will defrost much more permafrost than we thought. Every 1.8 degree F of additional warming would thaw one-quarter of the earth’s frozen tundra area — releasing staggering amounts of heat-trapping greenhouse gases (GHGs).
The feedback from just the CO2 released by the thawing permafrost alone (not including the methane) could add 1.5 degrees F to total global warming by 2100.Permafrost soils contain an estimated 1,700 GtC, almost twice the present atmospheric carbon pool. As permafrost soils thaw owing to climate warming, respiration of organic matter within these soils will transfer carbon to the atmosphere. This creates a feedback loop.
Models in which the carbon cycle is uncoupled from the atmosphere, together with one-dimensional models, suggest that permafrost soils could release 7 to 138 GtC by 2100. When a coupled global climate model is used, permafrost soils are predicted to release 68 to 508 GtC by 2100. Unfortunately, none of the models for the recent IPCC Fifth Assessment (AR5) of the climate by the world’s top scientists incorporates loss of the permafrost in their warming assessments (not to mention loss of the sea bed hydrates).
According to a March 2017 study, the Alaskan tundra is warming so quickly it has become a net emitter of carbon dioxide. Since CO2 is the primary heat-trapping greenhouse gas, this means a vicious cycle has begun that will speed up global warming. Warming soils will emit more CO2 and this will overwhelm any CO2 uptake due to an increase in plant life from CO2 fertilization and warmer temperatures.
Alaska, overall, was a net source of carbon to the atmosphere during 2012–2014. Data from NOAA’s Barrow Alaska station indicate that October through December emissions of CO2 from surrounding tundra increased by 73.4 percent since 1975. Early winter respiration is not well simulated by the Earth System Models used to forecast future carbon fluxes in recent climate assessments. Therefore, these assessments may underestimate the carbon release from Arctic soils in response to a warming climate. The study, based on aircraft measurements of carbon dioxide and methane and tower measurements from Barrow, Alaska, found that from 2012 through 2014, the state emitted the equivalent of 220 million tons of carbon dioxide gas (MtCO2e) into the atmosphere from biological sources (the figure excludes fossil fuel burning and wildfires). That’s an amount comparable to all the emissions from the U.S. commercial sector in a single year.
6. The Results
The recent (as of 2012) scientific literature says the key impacts we face in the coming decades if we stay anywhere near our current (as of 2012) emissions path include: 1) Staggeringly high temperature rise, especially over land — some 13 to 18 degrees F over much of the United States, 2) Permanent Dust Bowl conditions over the U.S. Southwest and many other heavily populated regions around the globe, 3) Sea level rise of around 1 foot by 2050, then 4 to 6 feet (or more) by 2100, rising some 6 to 12 inches (or more) each decade thereafter, 4) Massive species loss on land and sea — perhaps 50% to 70% or more of all biodiversity, 5) Unexpected impacts — the fearsome “unknown unknowns”, 6) Much more extreme weather, 7) Food insecurity — the increasingly difficult task of feeding 7 billion, then 8 billion, and then 9 billion people in a world with an ever-worsening climate, and Myriad direct health impacts.
Equilibrium climate sensitivity (ECS) is a measure of how much the global average temperature would increase if the CO2 concentration in the atmosphere were doubled and then stabilized (which ignores feedback from the doubling).
- When only factors that change significantly over a period of a decade are considered, called fast feedbacks (such as changes in water vapor, clouds and sea ice extent), it has been found to be 5 degrees F. This is called the Charney ECS.
- When slower feedbacks that change significantly over a period of a century are included (such as poleward expansion of forests, darkening and shrinking of ice sheets, and release of methane from thawing tundra and sea beds), the ECS is 11 degrees F for a doubling of the CO2 in the atmosphere (such as from 275 ppm, the pre-industrial level, to 550 ppm).
- A warming of 12 degrees F in the average global temperature would cause some areas of the world to surpass the wet-bulb temperature limit, and a 21-degree warming would put over half of the world’s population, as it is currently distributed, in an uninhabitable environment, due to the wet-bulb limit being surpassed. Eventual warming of 25 degrees F is feasible with a quadrupling of the CO2 concentration to 1100 ppm.
- Wet-bulb temperature is equivalent to what is felt when wet skin is exposed to moving air. It includes temperature and atmospheric humidity and is measured by covering a standard thermometer bulb with a wetted cloth and fully ventilating it. When the humidity is 100% the wet-bulb temperature is the same as the dry-bulb temperature, which is the temperature of the air.
- When the ambient temperature is excessive, humans and many animals cool themselves below ambient by evaporative cooling of sweat or saliva. In order for the heat dissipation process to work, the surrounding air must be cooler than the skin, which must be cooler than the core body temperature. The cooler skin is then able to absorb excess heat from the core and release it into the environment. If the wet-bulb temperature is warmer than the temperature of the skin, metabolic heat cannot be released and lethal overheating can ensue depending on the magnitude and duration of the heat stress.
- A sustained wet-bulb temperature of 95 degrees F over a period of at least 6 hours would be fatal even to fit and healthy people, naked in the shade, soaking wet and standing in front of a large fan; at this temperature our bodies switch from shedding heat to the environment, to gaining heat from it. For most people the maximum survivable wet-bulb temperature would be closer to 80 degrees F. An example of the threshold at which the human body is no longer able to cool itself and begins to overheat is a humidity level of 50% and a temperature of 115 degrees F, which would indicate a wet-bulb temperature of 95 degrees F. Such conditions would prevail across most of the land surface of the planet if human civilization burns enough fossil fuel to raise atmospheric levels of CO2 to 1100 ppm or more.
The 2015 Indian heat wave saw wet-bulb temperatures in Andhra Pradesh reach 86 degrees F. A similar wet-bulb temperature was reached during the 1995 Chicago heat wave. A heat wave in Iraq in August 2015 saw a wet-bulb temperature of 101.1 degrees F. During the 2017 Australian Heat Wave, wet-bulb temperatures at Badgery’s Creek in Western Sydney reached 88.7 degrees F on Feb 11, and 90 degrees F on Feb 12.
7. Where we are headed
The atmospheric CO2 concentration currently is 408 ppm and rising at the fastest rate ever.
The 2009 Copenhagen Climate Science Congress (attended by 2000 climate scientists) concluded that recent observations confirmed that, given the high rates of observed emissions, the worst-case IPCC scenario trajectories, (or even worse) were being realized.
The 2007 IPCC report, which began to consider amplifying carbon cycle feedbacks, warned that averaging 11 billion metric tons of carbon (GtC) emissions per year would lead to 1000 ppm of CO2 by 2100. The IPCC AR4 worst-case scenarios involved emissions well above an average of 15 GtC per year through 2100, so the atmospheric CO2 concentration would be well over 1000 ppm by 2100 in those scenarios.
Continuing on a business-as-usual path of energy use based on fossil fuels will raise it to 900 to 1100 ppm, or higher, by the end of this century. This rate of increase in atmospheric CO2 is unprecedented in Earth’s history.
CO2 levels haven’t been this high for 15 million years, when it was 5 to 10 degrees F warmer and seas were 75 to 120 feet higher.
8. Kansas and the interior
A 2009 NOAA-led report on U.S. climate impacts warns of scorching 9 to 11 degrees F warming over most of inland U.S. by 2090 with Kansas above 90 degrees F some 120 days a year, and that isn’t the worst case scenario, it’s based on a business-as-usual scenario. Two studies done around 2010 conclude that by century’s end, extreme temperatures of up to 122 degrees F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98 degrees F for some 60 days a year. Much of Arizona would be subjected to temperatures of 105 degrees F or more for 98 days out of the year — 14 full weeks. Yet that conclusion is based on studies of only 700 ppm and 850 ppm, so it would get hotter than that if levels of 1100 ppm or more are reached.
Coincidentally, while I was compiling my document the New York Magazine published their July 9th edition containing the article titled “The Uninhabitable Earth – Famine, economic collapse, a sun that cooks us: What climate change could wreak — sooner than you think” by David Wallace-Wells (http://nymag.com/daily/intelligencer/2017/07/climate-change-earth-too-hot-for-humans.html).
According to Joe Romm in his July 11th post, “New York Magazine has stirred up a firestorm of debate by publishing a worst-case scenario for climate change this week.
Responses range from Mashable’s ‘Do not accept New York Mag’s climate change doomsday scenario,’ to climatologist Michael Mann’s critical Facebook post, to Slate’s ‘New York Magazine’s global-warming horror story isn’t too scary. It’s not scary enough.’”
I read these new articles today and I recommend all three.
Another article related to this debate about how to persuade people regarding climate change, which I read a few days ago, is “Why U.S. Environmentalists Lost the Climate Change Fight” by Kevin Brass
My own view about the future is that the kind of aggressive government policy that is actually needed is unlikely to be implemented worldwide until the adults who are alive are likely to personally experience serious consequences from global warming during their lifetimes. I think the main uncertainty is whether we will have passed a tipping point by then, such as the point at which further warming will continue regardless of the level of additional anthropogenic CO2 emissions.
In regard to articles about doomsday scenarios, I still haven’t seen any that present a comprehensive worst-case scenario. Maybe this is because none of the computer models have yet to include all of the known potential feedbacks and risks, such as the CO2 and methane that could be released from thawing tundra and seabed hydrates, climate change induced infestations like the mountain pine beetle, which is destroying huge amounts of trees, and plagues resulting from the release of organisms, now trapped in ice sheets, that humans have never before experienced. Presenting a truly comprehensive worst-case scenario may simply be beyond our technical capability.
He estimated that by 2060 there would be 1.4 billion refugees (and 2 billion by 2100) due to rising sea levels. However, by 2060 we may also have large parts of the earth uninhabitable due to heat stress, and other large parts uninhabitable due to widespread permanent dust bowl conditions that make agriculture in those areas infeasible.
How many additional billions of refugees would those impacts cause?