Global warming may be happening faster than previously thought, according to a new study by a team of researchers including former NASA scientist James Hansen, whose testimony before Congress 35 years ago helped raise widespread awareness of climate change.
The study warns that the planet could exceed 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, of warming. This decadeCompared to the average temperature of pre-industrial days, the world will warm by 2 degrees Celsius by 2050. When countries signed the landmark Paris Agreement in 2015 to jointly fight climate change, they agreed to try to limit global warming to “well below” 2 degrees Celsius and a target of 1.5 degrees.
“A threshold of 1.5 degrees is deadlier than a doornail,” said Dr. Hanson said during a news conference on Thursday. The 2 degree target can still be achieved, but only with concerted action to stop using fossil fuels and at a much faster pace than current plans.
The world has warmed by about 1.2°C so far and is already experiencing worst heat waves, wildfires, storms, biodiversity loss and other effects of climate change. Exceeding the Paris Agreement temperature targets reflects the results of international diplomacy that, rather than precise scientific definitions, will result in significantly worse, more extreme and uncharted territory.
Experts generally do not care that the planet will soon exceed 1.5 degrees of warming. At our current rate of burning fossil fuels, the world is likely to exceed 1.5 degrees of warming within six years, according to a separate study published on Monday by British and Austrian scientists.
“I think everyone agrees that 1.5 degrees is in the rearview mirror at this point,” said Berkeley Earth Research Scientist Zeke Hausfather.
Dr. Housefather and others disagreed with Hansen’s team’s assessment of how sensitive the Earth’s climate is to greenhouse gases and, accordingly, how quickly the world would exceed 2 degrees of warming.
The new study analyzed reconstructed temperature and carbon dioxide levels over the past 66 million years, using evidence from other recent documents to calculate a numerical relationship between carbon dioxide and temperature. Global warming is driven by the burning of fossil fuels, which releases greenhouse gases like carbon dioxide into the atmosphere, where it traps the sun’s heat and warms the planet.
The researchers found that if the amount of carbon dioxide in the atmosphere doubled, the planet would warm by 3.6 to 5 degrees Celsius.
“This is very high in the range of estimates that exist in the academic literature today,” said Dr. Housefather.
Report of 2021 Intergovernmental Panel on Climate Change, Dr. Housefather contributed to this by saying that doubling carbon dioxide from pre-industrial levels would lead to between 2 and 5 degrees Celsius of warming, most likely around 3 degrees. The IPCC report brought together a range of estimates that scientists have come up with using a variety of methods, including climate models, historical data and reconstructions of Earth’s distant past.
So far, humans have increased the amount of carbon dioxide in the atmosphere by about 50 percent, from 280 parts per million in the 1700s to 417 parts per million in 2022—a relatively linear increase in temperature over time. But Dr Hansen believes warming is accelerating.
One reason is that countries and industries, especially shipping, have cracked down on air pollution in recent years, successfully reducing sulfate aerosols in the atmosphere. Different pollutants in the atmosphere have different effects. Sulfate aerosols, another byproduct of burning fossil fuels, reflect sunlight off Earth’s surface and help cool the planet slightly.
Despite these disagreements, the most realistic, physical timeframes of 1.5 and 2°C are, to a certain extent, irrelevant to how sensitive the Earth’s climate is to future greenhouse gas emissions. While the 1.5 degree target has already been missed, most experts agree that 2 degrees is still achievable – but not without more action than countries are currently taking.
“We are also going to pass 2 degrees. “That will become apparent unless we act to reduce the energy imbalance,” said Dr Hansen. “The first thing we need to do is reduce emissions as quickly as possible.”