For months, climate reports have been warning us that we must prevent the world from warming by 2 degrees Celsius (3.6 degrees Fahrenheit) in order to avoid the most disastrous effects of climate change. However, what policy makers and world leaders have failed to mention is that the world is less delicate than we think: CO2 emissions might not be so damaging to our climate.
As stated in the international treaty, the UN Framework Convention on Climate Change, the earth’s surface temperatures have increased by almost 0.8 degrees Celsius since 1850-1900, which means we only have a margin of 1.2 degrees Celsius before we reach the 2 degree cap.
Estimations by the Intergovernmental Panel on Climate Change (IPCC)‘s latest 2013 report were calculated using positive and negative models. If there is a massive drop in emissions, then the Earth might not reach the 2 degree mark; however, if coal-use and population growth both skyrocket, then we might meet the mark by 2040.
However, these estimates aren’t based on real-world models, and don’t take into account the sensitivity of our climate. According to the Wall Street Journal, “Climate sensitivity is defined as the global surface warming that occurs when the concentration of carbon dioxide in the atmosphere doubles.” If the climate is overly sensitive, then rising emissions will indeed push the world to the UN’s “dangerous” warming levels; if the climate isn’t overly sensitive, then emissions won’t have such a devastating impact on our environment, and it will take us longer to reach those ‘dangerous’ levels.
Climate reports using an observation-based energy-balance approach and global climate models have had different findings — even the IPCC’s report admitted the distinctions in the two models. With observation-based models, climate sensitivity projections are substantially less than global climate models’ projections. Observation-based energy balance models also take climate change’s 1998 hiatus into account, where we didn’t see a drastic rise in the Earth’s temperature.
The warming hiatus wasn’t considered in the IPCC’s 2007 report, which predicated that the world would warm by 0.2 degrees Celsius every 10 years in the beginning of the 21st century. With that in mind, can we trust climate reports that employ global climate models, rather than observation-based models? Why, then, are we on the fast track to implement policy that slashes emissions when we have room to explore economical ways to gradually lower our emissions? What’s the rush?
Climate sensitivity is something the public doesn’t often hear about, but is a fundamental aspect of the climate policy debate. Reports that take an observation-based approach show that human’s impact on our climate won’t cause the Earth to warm by 2 degrees, even by the end of the 21st century. Perhaps it’s time to re-evaluate our climate policies.
Developed and Written by Dr. Subodh Das and Tara Mahadevan
October 15, 2014
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