Global warming may be occurring at an accelerated pace, according to a recent study involving former NASA scientist James Hansen. The study suggests that the planet could surpass a 1.5-degree Celsius increase in temperature within this decade, compared to preindustrial levels, and could warm by 2 degrees Celsius by 2050. While countries agreed to limit global warming to “well below” 2 degrees Celsius in the Paris Agreement, Hansen believes that the 1.5-degree target is unlikely to be achieved without immediate and substantial action to reduce fossil fuel usage.
The Earth has already warmed by approximately 1.2 degrees Celsius, resulting in intensified heat waves, wildfires, storms, and biodiversity loss. Beyond the goals set in the Paris Agreement, the effects of climate change will worsen, leading to greater extremes and uncertainties.
Experts generally agree that the planet is on track to surpass the 1.5-degree warming threshold. Another study by British and Austrian scientists supports this finding, predicting that the 1.5-degree mark will be reached within the next six years at the current rate of fossil fuel consumption.
While experts agree on the inevitability of surpassing 1.5 degrees of warming, they differ in their assessments of the sensitivity of the Earth’s climate to greenhouse gases and the timing of reaching 2 degrees of warming. To estimate this, the recent study analyzed historical temperatures and carbon dioxide levels over millions of years and established a relationship between carbon dioxide and temperature. It concluded that doubling the amount of carbon dioxide in the atmosphere would lead to a temperature increase of 3.6 to 5 degrees Celsius.
However, some experts, including Dr. Zeke Hausfather, argue that the Hansen team’s estimate is on the high end of current academic estimates. A 2021 report from the Intergovernmental Panel on Climate Change projected a temperature increase of 2 to 5 degrees Celsius from doubling carbon dioxide levels, with the most likely outcome around 3 degrees. Regardless, the Earth’s current carbon dioxide levels have already increased by approximately 50 percent, from 280 parts per million to 417 parts per million, resulting in a linear temperature rise.
Dr. Hansen attributes the accelerating pace of warming to the reduction in sulfate aerosols in the atmosphere, which reflect sunlight and slightly cool the planet. As countries and industries have taken measures to reduce air pollution, such as cracking down on shipping emissions, the absence of sulfate aerosols has contributed to increased warming.
Despite disagreements over climate sensitivity, the deadlines of 1.5 and 2 degrees Celsius are approaching rapidly. Most experts agree that while the 1.5-degree goal has already been missed, achieving a 2-degree limit is still possible but would require significant action beyond current efforts.
Dr. Hansen emphasizes the need to reduce emissions as quickly as possible to mitigate the impending temperature increase.