How Important Is the Paris Climate Agreement?
What is the Paris Agreement? How important is it to climate change?
Last week, the president of the United States announced his decision to withdraw the US from the Paris Climate Agreement, which it helped write. The US would join only two of nearly 200 other countries who have not signed the Agreement: Nicaragua, whose envoy has claimed the Agreement does not go far enough and has vowed to combat climate change outside of the Agreement, and Syria, a country currently embroiled in a devastating civil war.
According to a nationally representative poll from the Yale Program on Climate Change Communication, 7 in 10 voters in the US support staying in the Agreement. There are many complex and interwoven social, political and economic reasons to consider when evaluating participation in the Agreement, but here at Ask Science we focus on the explanations that science provides for the world around us.
In his speech announcing the US withdrawal, the president stated, “Even if the Paris Agreement were implemented in full, with total compliance from all nations, it is estimated it would only produce a two-tenths of one degree Celsius reduction in global temperature by the year 2100.” Let’s take a closer look at this claim and the study that came to this conclusion. Are the terms of the Paris Agreement really that ineffective? How much impact is the Agreement expected to have?
The Paris Climate Agreement
The Paris Climate Agreement was drafted by representatives from 196 countries at the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change and adopted in December of 2015. Under the Agreement, each country determines its own plan to mitigate global warming, mainly through cutting carbon dioxide emissions and other emissions from fossil fuels. The signatories work together with the goal of limiting global warming to 2 degrees Celsius or less by 2100.
The United States emits the second highest number of million metric tons of carbon dioxide annually and is responsible for, together with Europe, more than half of the cumulative carbon emissions since the Industrial Revolution. Under the Paris Climate Agreement, the US pledged to reduce emissions by 26-28% from 2005 levels by the year 2025.
The Paris Agreement has been called “a triumph for evidence-based decision making”, “a trade agreement”, and “an investment blueprint and a strong incentive for innovation in the energy and the economy of the future”.
Should we really worry about just a few degrees?
A difference of 2 degrees Celsius (~3.5 degrees Fahrenheit) may not seem like much so the importance of a 2 degree limit versus a 1 degree or a 3 degree limit increase is not obvious. Predictions are also challenging since climate models must not only incorporate a complicated set of natural climate checks and balances but also expectations of human behavior in emissions.
A study recently published in Nature attempted to track the different impacts predicted (averaged over a few climate models) for 1.5 versus 2 degrees of warming. Their findings suggest that even a difference of 0.5 degrees is expected to have a noticeable impact on our environment and thus our way of life, including 2 meters more of sea level rise, almost twice the probability of an increase in global extreme temperature events, and between one and one-third to twice the percentage decrease in local maize, wheat, rice, and soy yields for present-day tropical agricultural areas.
Thus, even a difference of half of a degree is expected to produce noticeable impacts that will require adaptation. The authors also note that the majority of emission scenarios (i.e. ignoring the Paris Agreement versus complying with minimums set by the Paris Agreement) still exceed the 1.5 degree limit before 2100.
How much can the Agreement actually curb temperatures?
Let’s return to the president’s concern that the Paris Climate Agreement would only produce two-tenths of a degree of impact on global temperatures by 2100. The statistic has been linked to an MIT study conducted in 2016 called “How much of a difference will the Paris Agreement make?”
In the publication, the authors do indeed stress that the Paris Agreement is only a first step towards curbing rising global temperatures. Specifically they state that “even under the same level of commitment of the Paris Agreement after 2030, our study indicates a 95% probability that the world will warm by more than 2 degrees Celsius by 2100”.
The study found that global warming would slow by a predicted 0.6 to 1.1 degrees Celsius by 2100 if all countries followed through with the pledges made in the Paris Agreement. However, within the framework of the Agreement, these pledges are only made through 2030. There is, of course, a possibility that countries will strengthen their commitments further capping the rise in global temperatures.
The more pessimistic 0.2 degree limit cited by the president is not the expected difference between implementing the Paris Agreement and no climate policy at all, as was suggested in his speech. The study instead notes that the implementation of the Paris Agreement would decrease the average global temperature by 0.2 degrees more relative to the earlier Copenhagen agreement. The researchers on the study have further stated that “the Paris Agreement is an unprecedented and vital effort by nearly 200 countries to respond to the urgent threat of global climate change.”
The impact of the US decision to withdraw remains to be seen. Will the administration take a different approach to tackling climate change by focusing on innovation in the growing area of clean energy and negative emissions technologies? Will inaction on the part of the US encourage other countries to fall short of their pledges to cut emissions? For opinions on the importance of the US decision, check out the collection of reactions from scientists and politicians published in the journal Science and from scientists published in the journal Nature.
Whatever your opinion on the Paris Agreement – it goes too far, it does not go far enough – the complexity of climate change and our approach to mitigating its effects requires that we take care in the interpretation of the related scientific and economic research and leave our bias at the door.
Until next time, this is Sabrina Stierwalt with Ask Science’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.comcreate new email.
Image courtesy of shutterstock.
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About the Author
Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.
