New pledges could eliminate the worst climate outcomes

Ahead of the United Nations climate change conference (COP26), more than 100 countries pledged to decrease greenhouse gas emissions. In a new study published in the journal Science, experts analyzed these pledges – known as nationally determined commitments (NDCs) – and assessed how they would potentially affect Earth’s climate. 

According to the study authors, the current NDCs could pave the way for reducing global warming to two degrees Celsius (3.6 degrees Fahrenheit) or less during this century.

Based on the pledges made at the 2015 Paris Agreement, the researchers determined that the possibility of limiting temperature rise to below 2 and 1.5 degrees Celsius by 2100 was 8 and 0 percent, respectively. Now, based on the new pledges, the study authors estimate that these possibilities have risen to 34 and 1.5 percent. 

The experts emphasize that these percentages can be achieved only with supporting policies and measures of equal or greater ambition. Furthermore, they say these odds can increase to 60 and 11 percent, respectively, if countries pursue a more ambitious route after 2030.

Such a scenario could also eliminate the possibility of global temperature rise exceeding four degrees Celsius. The chance of such an increase was 10 percent higher under the 2015 commitments. 

“We are so much closer to getting to the 2-degree goal than six years ago when the Paris Agreement was first signed. The wave of strengthened climate pledges and net-zero targets significantly increased our chance of staying under 2 degrees Celsius. And we practically ruled out the possibility of the worst climate outcomes of 4 degrees or higher,” said study co-author Haewon McJeon, a research scientist at the Department of Energy’s Pacific Northwest National Laboratory. 

Study lead author Yang Ou, a postdoctoral researcher at the Joint Global Change Research Institute, stated that there is a one in three chance to meet the 2 degrees Celsius limit, but making the 1.5 degree Celsius limit more plausible will need more ambition.

The study evaluated a range of emissions scenarios, using an open-source model called the Global Change Analysis Model (GCAM). The scientists ran multiple scenarios, including a hypothetical future in which prevailing climate mitigation measures and policies remain mostly unchanged through 2100.

According to the study authors, various factors impacted near-term emissions trajectories and long-term climatic outcomes. One example is the worldwide shift away from coal in favor of technology advancements that reduced the cost of solar panels and electric automobiles. They claimed that these innovations had aided in bringing the Paris Agreement’s goals closer to realisation.

“New commitments, technological advances, and the near- and long-term recovery from the pandemic have set us on a different course than what laid before us at the 2015 Paris Agreement. But if we adopt more ambitious goals that truly reflect the common but differentiated responsibilities across all parties, that gives us a better than even chance of staying under 2 degrees Celsius,” said study co-lead author Gokul Iyer.

“And this highlights the importance of the Glasgow meeting. Without periodic and transparent updates, we won’t get the commitments strong enough to meet the temperature goal.”

The study is published in the journal Science.

—

By Ashikha Raoof, Earth.com Staff Writer