Our governments appear to be abandoning the fight to mitigate and adapt to climate change, largely fuelled by Donald Trump, who has declared the subject “a Chinese hoax.” The reality is far different. Fortunately, scientists are not so foolish and continue to collect data that shows a need for coordinated and collective action.
Foremost are papers that present evidence to indicate global warming is accelerating. An article appearing last year in the journal Environment: Science and Policy for Sustainable Development provides statistics of concern to all of us. It shows that a 0.4°C (0.72°F) rise has occurred in the past two years, with atmospheric warming accelerating by more than 50% since 2010.
Published on February 3, 2025, its lead author is James Hansen, former Director of NASA’s Goddard Institute for Space Studies, and current Director of the Climate Science, Awareness and Solutions Program at Columbia University’s Earth Institute. Co-authors include other climate scientists from Columbia, Yeshiva University, NASA, CSAS Korea, the University of Kansas, UC-Irvine, Mercator Ocean International, the European Academy of Sciences, Peking University, Operaatio Arktis and the Club of Rome Netherlands. Unlike Trump, all these authors declare no conflicts of interest with credentials far more credible than those of the President of the United States and his acolytes.
Compound Drought and Heat Waves on the Rise
In addition to the Hansen et al. article, other recent studies and reports have sounded similar alarm bells. One appearing in the journal Science Advances describes the rise in compound drought and heat events (CDHEs) surging around the world since the early 2000s, with global areas affected doubling between 1980 and 2001 and 2002 to 2023. The overall trend suggests that our atmosphere will warm more than 1.5°C before 2030, well ahead of the projections first described in the run-up to the 2015 Paris Climate Agreement.
Warming Atmosphere, Warming Oceans
When the atmosphere warms, the ocean surface does as well and in the high Arctic, that means sea ice melt releases freshwater to flow south, over the heavier, warmer salt water that is delivered to the North Atlantic Ocean by the Atlantic Meridional Overturning Circulation (AMOC). AMOC produces the Gulf Stream and the North Atlantic Drift. The former warms the U.S. East Coast while the latter keeps Western European temperatures higher than the latitude would suggest. That cold freshwater release could shut AMOC down in the next 30 years, based on the latest Hansen et al. paper. AMOC’s shutdown has been described by climatologists as a point of no return for the climate, leading to large sea level rises.
Earlier Intergovernmental Panel on Climate Change (IPCC) reports tabled at annual COP events have predicted an AMOC shutdown unlikely this century. A 2025 joint University of Washington and Caltech study appearing in Nature Geoscience also predicts changes to AMOC, but not to the same extent as the Hansen et al. paper projects. It predicts AMOC will weaken between 18 and 43% by the end of the 21st century. That is likely not to cause AMOC to shut down. If the projections depicted by Hansen et al., however, prove more accurate, Arctic ice will continue to melt faster than previously predicted, not just affecting the North Atlantic but also the North Pacific Ocean.
The difference between these two studies is stark. The Hansen et al. study suggests a coming catastrophe. The Washington and Caltech study predicts AMOC slowing but no collapse. Even if the latter proves to be a better representation of the future, it will lead to cooler and drier climates in Europe and greater cold in Scandinavia. It will also impact the Amazon rainforest basin as tropical Atlantic sea temperatures continue to rise, with a potential positive to neutral impact on precipitation. In terms of sea level rise, the Washington and Caltech study suggests less than a 30-centimetre (approximately one foot) increase by 2100.
Southern Hemisphere and Southern Ocean Climate Change
The Southern Ocean, other than a few islands, sees no landfall. It lies between Tasmania, Cape Horn, the Cape of Good Hope, and Antarctica. Based on 75 years of collected data from a weather station on Macquarie Island, one of the few landfalls, precipitation levels over the Southern Ocean are rising as atmospheric warming moves storm tracks closer to Antarctica.
More rain means more freshwater in the upper layers of the Southern Ocean. This increase, combined with continental ice melt from Antarctica, is cooling the ocean surface by as much as 10 to 15% since 1979.
The global ocean plays an important role as a carbon sink. It has absorbed more than 25% of anthropogenic CO2 emissions since the 1960s, with the amount absorbed increasing as atmospheric CO2 concentrations have risen. With freshwater additions to the surface, CO2 outgassing from evaporation is slowing even though the Southern Ocean is sweating more in response to increased rainfall from atmospheric warming.
What impact have changes to the Southern Ocean’s climate had on Australia, South America, Southern Africa and Pacific island nations? The freshening and warming are intensifying extreme heat events in Western Australia while reducing rainfall by as much as 50%. Ocean current patterns around Australia are changing with the East Australian Current strengthening, contributing to accelerated sea level rise.
Meanwhile, Pacific island nations continue to see changes in wind patterns and rising sea levels, making places like Tuvalu increasingly uninhabitable.
In South America, changes to the Southern Ocean circulation and freshening are reaching as far north as Brazil, linked to northeastern increases in precipitation. In southern Africa, freshening of the Southern Ocean is causing variability in ocean currents while moving rainfall south of the continent. Even Africa’s Sahel is being impacted by Southern Ocean changes, which have been linked to rising drought risk.
