Royal Society Special Issue on Global Warming Details ‘Hellish Vision’ of 7°F (4°C) World — Which We May Face in the 2060s!

http://thinkprogress.org/romm/2011/06/02/234291/romm/2011/01/13/207334/science-kiehl-ncar-paleoclimate-lessons-from-earths-hot-past/

by Joe Romm Posted on June 2, 2011

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. So much of what the public and policymakers think is coming is a combination of

The low end of the expected range of warming and impacts based on aggressive policies to reduce emissions (and no serious carbon-cycle feedbacks)
Analyses of a few selected impacts, but not an integrated examination of multiple impacts
Disinformation pushed by the anti-science, pro-pollution crowd

In fairness, a key reason the scientific community hasn’t studied the high emissions scenarios much until recently because they never thought humanity would be so self-destructive as to ignore their warnings for so long, which has put us on the highest emissions path

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Warming of 7F is certainly not the worst-case in the scientific literature (see M.I.T. doubles its 2095 warming projection to 10°F “” with 866 ppm and Arctic warming of 20°F and “Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year “” and that isn’t the worst case, it’s business as usual!“).

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But for the first time, “A hellish vision of a world warmed by 4C within a lifetime has been set out by an international team of scientists,” as the UK’s Guardian describes it:

A 4C rise in the planet’s temperature would see severe droughts across the world and millions of migrants seeking refuge as their food supplies collapse.

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What is “worst-case” is that if we stay on the high emissions pathway and the carbon cycle feedbacks turn out to be strong (as observations and paleoclimate data suggest they will be) then it could happen by the 2060s. It could look something like this [temperature in degrees Celsius, multiple by 1.8 for Fahrenheit]:

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Also, while Betts et al. does a better job of incorporating carbon-cycle feedbacks into their modeling than virtually anyone else, I do not believe that they incorporate any feedback of methane emissions from the tundra or methane hydrates — and that is certainly the most worrisome of all of the carbon-cycle feedbacks

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… a 4°C world would be facing enormous adaptation challenges in the agricultural sector, with large areas of cropland becoming unsuitable for cultivation, and declining agricultural yields. This world would also rapidly be losing its ecosystem services, owing to large losses in biodiversity, forests, coastal wetlands, mangroves and saltmarshes, and terrestrial carbon stores, supported by an acidified and potentially dysfunctional marine ecosystem. Drought and desertification would be widespread, with large numbers of people experiencing increased water stress, and others experiencing changes in seasonality of water supply. There would be a need to shift agricultural cropping to new areas, impinging on unmanaged ecosystems and decreasing their resilience; and large-scale adaptation to sea-level rise would be necessary. Human and natural systems would be subject to increasing levels of agricultural pests and diseases, and increases in the frequency and intensity of extreme weather events.

In such a 4°C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved. Even though some studies have suggested that adaptation in some areas might still be feasible for human systems, such assessments have generally not taken into account lost ecosystem services.

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In the coming decades, one of the most serious impacts of climate change is projected to be the consequences of the projected increases in extreme weather events. For example, climate change-induced changes in precipitation patterns and changes in climate variability would increase the area of the globe experiencing drought at any one time from today’s 1 per cent to a future 30 per cent by the end of the twenty-first century…

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Only a few days of high temperatures near flowering in wheat, groundnut and soybean can drastically reduce yield, while maize losses could potentially double owing to floods in the USA; and the AVOID study estimated that, in a 4°C (7.2°F) world, 50 per cent of fluvial flood-prone people would be exposed to increased flood risk compared with approximately 25 per cent in a 2°C (3.6°F) world.

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However, this paper is not intended as a message of futility, but rather a bare and perhaps brutal assessment of where our ‘rose-tinted’ and well intentioned (though ultimately ineffective) approach to climate change has brought us. Real hope and opportunity, if it is to arise at all, will do so from a raw and dispassionate assessment of the scale of the challenge faced by the global community. This paper is intended as a small contribution to such a vision and future of hope.

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responses that might be most appropriate for a 2°C world may be maladaptive in a +4°C world; this is, particularly, an issue for decisions with a long lifetime, which have to be made before there is greater clarity on the amount of climate change that will be experienced. For example, a reservoir built to help communities adapt to moderate temperature increases may become dry if they continue to increase, or coastal protection designed for 2°C may be overcome at 4°C. This will require systems that are flexible and robust to a range of possible futures. Third, for some of the more vulnerable regions, a +4°C world may require a complete transformation in many aspects of society, rather than adaptation of existing activities, for example, high crop failure frequency in southern Africa may require shifts to entirely new crops and farming methods, or SLR (sea level rise) may require the relocation of cities.

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it must always be repeated that for far, far less than the cost of so-called adaptation, we could dramatically reduce the likelihood of the worst of these impacts with technologies are available today or in the process of being commercialized.

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Indeed, while one paper cited above asserts, “There is now little to no chance of maintaining the rise in global mean surface temperature at below 2°C,” that is only true in the political sense that the human race is choosing not to act, choosing not to stay below 2°C. We almost certainly have it within our scientific and technological power to do so, though it would take a WWII-scale effort globally
[In other words, we are too stupid.]

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