Tom Giesen writes in a guest column for Informed Comment:
Global warming’s disasters once seemed far off and science-fictional. It is now becoming clear to the scientific community that, to the contrary, very bad things could happen beginning relatively soon. For Baby Boomers, from the the Cuban Missile Crisis or the assassination of John F. Kennedy in the early 1960s till now does not seem like such a long period of time. But in a similar span of years, taking us to about 2060, the world could well experience an increase in global average temperatures of some 4 degrees Centigrade. If we consider the likely effects of this steep warming trend carefully, it becomes clear that the resulting “four degrees” world (as scientists call it) is far less hospitable for humans than our own, a world so inhospitable that we must avoid creating it at any cost.
This rapid change in the earth’s climate is being caused by massive dumping of carbon dioxide into the atmosphere, mainly by industrialized societies. Cutting back on carbon dioxide emissions has to date been an abject failure. Political leaders have, in general, taken the position that cut-backs must happen, but “not during my term of office”. About half of emissions are produced by about 1% of the population. 70,000,000 people are the problem. Because you are reading this, the odds are that you are part of that 1 percent.
If every country in the world actually met its pledges to limit or cut back on emissions, it is not impossible that in 2060 the temperature increase will be only 3 degrees C. But we’d likely get to the “four degree world” by 2100. If the world’s nations do not meet their pledges, warming by 4 degrees C. may occur even earlier, by 2060. Those are not end-points in warming; they are snapshots. Warming is a continuous process, not an event.
A four degree-extra (C.) world does not sound so bad on the surface, especially to Americans used to Fahrenheit. But for them, it actually could be a 7 degree-extra (F.) world in 2060, and it won’t be nice. Remember that the extra heat is not distributed equally everywhere.
Consider these scenarios, thought highly likely by scientists:
A temperature increase of 4 degrees C. will cause a 40% reduction in corn and rice crops, and loss of other agricultural produce, as well. The world doesn’t have fewer mouths to feed over time, and a decline in these key staples will likely produce widespread starvation..
People will be forced from their homes, like so many Syrian refugees, on a grand scale — from coastal areas because of rising seas; from areas no longer habitable due to high temperatures or drought; and from changing industrial and commercial practices.
Other effects include ice melting, weather extremes, ocean acidification, loss of coral reefs, changes in stream flows, large losses in biodiversity, water shortages, forest dieback and fires, and so on – the list is very long.
A temperature increase of 4 degrees C is now thought likely to cause the disintegration of an organized global community. A four degree world will likely be so altered that human society cannot adapt to it.
Temperatures are lower over the oceans (70% of global area), which absorb heat and carbon dioxide. Over land they are higher. So a 4 degrees C.-extra world would actually imply the following:
Up to 6 degrees C (10.8 degrees F.) average increase over land;
Up to 8 degrees C (14.4 degrees F.) increase over China;
Up to 10 degrees C (18 degrees F.) increase over central Europe;
Up to 12 degrees C (21.6 degrees F.) increase over New York City (and people think they have to flee to the Hamptons in August now!)
Scientists have been warning about global warming since the middle of the last century; James Hansen of NASA’s Goddard Space Center addressed Congress on the topic in 1988. A policy goal established in the 1990s, based on scientific evidence at the time, was to hold warming at 2 degrees C above the preindustrial (~ 1850) average. In 2002, a policy of “preventing dangerous anthropogenic [i.e. human-caused] interference with the climate system” was adopted by the United Natioins, and 2 degrees C of warming was the maximum allowable.
Mitigation of warming via reduced emissions has been a global goal, but very little of practical value has been accomplished. Emission levels continue to rise, and hence the concentration of greenhouse gasses in the atmosphere is rising as well. CO2 concentrations in the atmosphere recently reached 391 parts per million (ppm); the preindustrial level was 278; the increase is 40.6%. The global average temperature has now increased by almost 1 degree C above the preindustrial average.
Recent scientific papers have shown that the impacts of a 2 degrees C. rise are much greater than were indicated earlier. Impacts for a 1 degrees C. rise are now expected to be as great as those previously assumed for a 2 degrees C. rise. Worse, there is a scientific consensus today that holding warming to 2 degrees C is no longer possible given the emissions to date and the failure to cut back. Hence, avoiding dangerous human-caused interference with the climate system is no longer possible. Now the question is, to what level will global average temperatures increase by (say) 2060, and at what time, temperature and total emissions will the global temperature average peak?
While total historic emissions were disproportionately caused in recent history by the United States, China’s current annual emissions are the highest of any nation and are growing faster than any other large polluter.
Recent global emissions increases include:
1990s: 2.7% increase in emissions each year (average)
2000 – 2007: 3.5%/year
2009 – 2010: 5.6%/year
Can this nightmare any longer be averted?
To limit the maximum global average temperature rise from warming to 4 degrees C, we must reduce emissions 3.5 % per year – now. To be specific, we must reduce global emissions 3.5% in 2013 and each year thereafter. If China and others do not agree to do that, the rest of the world must reduce more to compensate, for an annual reduction globally of 3.5%. Postponing any annual reduction appears to be a fatal mistake, as we have seen – it is tacit admission that missing targets is OK. Missing targets is not OK.
Admittedly, a 3.5% annual reduction in fossil fuel energy use may initially be hard on the economies of the industrial and industrializing countries. Fossil fuels provide 87 percent of our energy. But solar, wind, geothermal and other alternatives are increasingly competitive, and big governmental programs to implement them could pump more money into economies now suffering from austerity policies, and increase employment. But even if it is economically painful, we must do it anyway. Winning World War II required drafting millions and massive government requisitions from factories, as well as a Manhattan Project to develop an atomic bomb before the Nazis did. We face a far more dangerous enemy today than the Axis of fascist states. We face a threat to life as we know it. A four degree world is worse than some temporary economic slowdown, and it is the fate staring us in the face if we go on with business as usual. We must start actually reducing our carbon dioxide production on January 1, 2013.
Sources for the above:
The World Bank. 2012. Turn down the heat: why a 4 degree warmer world must be avoided. A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics.
Anderson and Bows. 2010. Beyond ‘dangerous’ climate change: emission scenarios for a new world. Phil. Trans. R. Soc. A. 369 20-44.
Anderson, Kevin. 2011. Climate change – going beyond dangerous. Brutal numbers and tenuous hope or cognitive dissonance. Tyndall Centre. U Manchester. A slideshare found at: http://www.slideshare.net/DFID/professor-kevin-anderson-climate-change-going-beyond-dangerous?from=share_email
International Energy Agency. 2012. World Energy Outlook 2012. Executive Summary.
 Note: 1o C = 1.8 dgree F; 3°C = 5.4 degree F; 4 degrees C = 7.2 degrees F, etc.
 In theory, 2 degrees C can be accomplished with reductions in emissions of 40% by 2015, 70% by 2020, and 90% by 2030. That scenario is not thought realistic; it could bring economic activity to a halt, and is not thought politically feasible.
 Energy availability interacts intimately with global warming. However, uncertainties with regard to energy availability preclude considering it here.
Tom Giesen has a BA, MFA, MS (forest biogeochemistry), and has been teaching a course on Global Change at the University of Oregon as an adjunct.