Climate change is accelerating, scientists find in ‘grim’ report » Yale Climate Connections

The amount of heat trapped by climate-warming pollution in our atmosphere is continuing to increase, the planet’s sea levels are rising at an accelerating rate, and the Paris agreement’s ambitious 1.5°C target is on the verge of being breached, according to a recent report by the world’s top climate scientists.

“The news is grim,” said study co-author Zeke Hausfather, a former Yale Climate Connections contributor, on Bluesky.

A team of over 60 international scientists published the latest edition of an annual report updating key metrics that are used in reports of the Intergovernmental Panel on Climate Change, the leading international scientific authority on climate change.

Earth out of balance

Climate change is caused by variations in Earth’s energy balance – the difference between the planet’s incoming and outgoing energy. Nearly all incoming energy originates from the sun. The Earth absorbs that sunlight and sends it back out toward space in the form of infrared light, or heat. Greenhouse gases such as carbon dioxide absorb infrared light, and so increased levels in those gases trap more heat in the atmosphere, warming the planet’s surface and oceans.

The new report finds that as a result of this increasing greenhouse effect, Earth’s energy imbalance has been consistently rising every decade. In fact, the global imbalance has more than doubled just since the 1980s. And from 2020 to 2024, humans exacerbated the problem by adding about 200 billion more tons of carbon dioxide-equivalent greenhouse gases to the atmosphere.

This increase in trapped energy has continued to warm Earth’s surface temperatures. The new study estimated that at current rates, humans will burn enough fossil fuels and release enough climate pollution to commit the planet to over 1.5°C of global warming above preindustrial temperatures within about three more years, in 2028.

The most recent report from the Intergovernmental Panel on Climate Change, published in 2021, concluded that average temperatures had increased 1.09°C since the late 1800s. The new study updates this number to 1.24°C, driven largely by the record-shattering hot years of 2023 and 2024.

The paper also finds that global surface temperatures are warming at a rate of about 0.27°C per decade. That’s nearly 50% faster than the close to 0.2°C-per-decade warming rate of the 1990s and 2000s, indicating an acceleration of global warming.

That warming causes the water in the ocean to expand and land-based ice to melt, both of which contribute to rising sea levels. Since 1900, global sea levels have risen by nine inches, at an average rate of 1.85 millimeters per year. But the rate of sea level rise since 2000 has been twice as fast, at 3.7 millimeters per year. And over the past decade it’s risen faster yet, at 4.5 millimeters per year. In other words, sea level rise is also accelerating.

“Unfortunately, the unprecedented rates of global warming and accelerating sea-level rise are as expected from greenhouse emissions being at an all-time high,” University of Leeds climate scientist and the study’s lead author Piers Forster wrote by email.

A thin silver lining

Most, but not all, of the findings in the new paper are grim. For example, although humanity will almost certainly miss the more ambitious 1.5°C target in the Paris agreement, the study finds that its primary target of limiting global warming to 2°C remains within reach. At current emissions rates, 2°C global warming will be breached around midcentury, but that still leaves several decades to bring emissions down.

“Future emissions control future warming,” Forster said. “And if the world were to rapidly act on carbon dioxide and methane emissions, we could halve the rate of warming.”

The study identifies glimmers of hope that climate policies and solutions around the world could soon begin to move emissions in this direction.

“I think there is not much silver lining in the report per se given the apparent acceleration of warming,” Hausfather said in an email to Yale Climate Connections. “But I would note that global CO2 emissions have slowed notably over the past 15 years or so, and the cost of clean energy continues to fall. We are clearly moving away from the worst-case emissions scenarios, even if we are still heading toward potentially catastrophic warming of 3°C by 2100.”

China will be a key player in determining the future evolution of Earth’s climate. Because of its large population and rapid economic growth, China is responsible for nearly one-third of global climate pollution. But as the result of a rapid deployment of clean technologies, China’s emissions have begun to slightly decline over the past year.

“This is also the decade when global [greenhouse gas] emissions could be expected to peak and begin to substantially decline,” the report’s authors conclude. “Depending on the societal choices made in this critical decade, a continued series of these annual updates could track an improving trend.”