Monday began with another round of disturbing news about the rising average world temperature, and the picture did not improve as the week wore on.
In 2015, partly as a result of pressure from the most vulnerable nations, signatories of the Paris Climate Accords agreed to work to keep the rise of the average world temperature to no more than 1.5° Celsius (2.7° Fahrenheit) compared with the 1850-1900 period. All along, it was recognized that achieving this goal would be dauntingly difficult, technically possible but probably out of reach politically. The Intergovernmental Panel on Climate Change’s 2018 special report, which I wrote about here, voiced guarded optimism that the goal could be attained. But it stated that success would require "deep emissions reductions" and "rapid, far-reaching and unprecedented changes in all aspects of society."
This was followed in 2022 by the IPCC’s Emissions Gap Report, which noted
Policies currently in place point to a 2.8°C temperature rise by the end of the century. Implementation of the current pledges will only reduce this to a 2.4-2.6°C temperature rise by the end of the century for conditional and unconditional pledges respectively.
The report finds that only an urgent system-wide transformation can deliver the enormous cuts needed to limit greenhouse gas emissions by 2030: 45 per cent compared with projections based on policies currently in place to get on track to 1.5°C and 30 per cent for 2°C. This report provides an in-depth exploration of how to deliver this transformation, looking at the required actions in the electricity supply, industry, transport and buildings sectors, and the food and financial systems.
Since then, while some scientists still say the 1.5° goal can be attained, there are fewer and fewer expressing such optimism. The carbon dioxide load in the atmosphere continues to accumulate, the threat of potent methane releases appears to be rising, and, if not upgraded, the currently inadequate national pledges to cut greenhouse emissions will deliver us into the dystopian zone of the worst case scenarios posited in the IPCC’s six detailed climate assessments over the past 34 years. The burning of fossil fuels emitted record levels of greenhouse gases into the atmosphere in 2023, according to the Global Carbon Project.
The week began with publication of a study in the peer-reviewed Nature Climate Change saying that so far the average world temperature rise over the preindustrial era is not the 1.2°C (2.16°F) that scientists say has already occurred but rather 1.7°C (3.02°F). If that proves to be true, it means global warming is running 20 years faster than the IPCC’s latest projection, and 2°C (3.6°F) can’t be far behind.
At Grist, Brian Ng wrote:
Even more surprising than the findings, perhaps, is the fact that they were derived from the study of sea sponges. A research team led by Professor Malcolm McCulloch of the University Western Australia Oceans Institute analyzed sclerosponges, a primitive orange sponge species found clinging to cave roofs deep in the ocean. Sclerosponges grow extremely slowly — just a fraction of a millimeter a year — and can live for hundreds of years. This longevity is part of why they can be particularly valuable sources of climate data, given that our understanding of ocean temperatures before 1900 is very hazy.
By taking samples from these sponges, McCulloch’s team was able to calculate strontium to calcium ratios, which can be used to derive water temperature back into the 1700s. These ratios were then mapped onto existing global average water temperature data so that the team could fill the holes we have at the beginning of the industrial period, when humans began releasing large amounts of carbon dioxide into the atmosphere.
Given how well the information gleaned from the sponges matches ocean temperature records from recent decades, the researchers were able to support extrapolating far into the past to show that the average ocean temperature was lower than the IPCC supposes.
How convincing their small sample will be to other scientists is yet to be determined. While the study passed the peer review process, Hali Kilbourne, a geological oceanographer at the University of Maryland Center for Environmental Science, told The New York Times, “I would want to include more records before claiming a global temperature reconstruction.”
Meanwhile, the EU’s Copernicus Climate Change Service (C3S) and the European Center for Medium-Range Weather Forecasts announced Thursday that the world just had the hottest January ever recorded. It was also the eighth consecutive month exceeding historic temperatures. And it was 12th consecutive month that the overall average temperature was above 1.5°C.
In a statement, C3S deputy director Samantha Burgess said: "2024 starts with another record-breaking month—not only is it the warmest January on record, but we have also just experienced a 12-month period of more than 1.5°C above the preindustrial reference period. Rapid reductions in greenhouse gas emissions are the only way to stop global temperatures increasing." You may have heard that prescription a few times previously.
Former Intergovernmental Panel on Climate Change chair Bob Watson told BBC Radio 4's "Today" program that the last 12 months "far exceeds anything that is acceptable. Look what's happened this year with only 1.5°C. We've seen floods, we've seen droughts, we've seen heatwaves and wildfires all over the world."
Shannon Osaka at The Washington Post reported
Does this mean we have missed the 1.5C climate goal? No. There’s actually some disagreement about what exactly counts as breaching that threshold — but scientists and policymakers agree that it has to be a multiyear average, not a single 12-month period. Scientists estimate that without dramatic emissions reductions, that will happen sometime in the 2030s. But there could be other single years or 12-month periods that cross the line before then.
In the next 12 to 18 months, we will see how much of the breaching of the 1.5°C threshold this past year was a consequence of El Niño adding its heat to the overall global warming trend. What we do know for certain is that without concerted effort now—ranging from backyard gardeners to world leaders—1.5°C, even a disastrous 2.0°C, will look like bliss compared with where we may wind up.