How Important Is the Paris Climate Agreement?

What is the Paris Agreement? How important is it to climate change?

Sabrina Stierwalt, PhD
4-minute read
Episode #241

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.


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About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.