“The ultimate test of climate projections is to compare them with what has played out…” says earth sciences professor Torbjörn Törnqvist, lead author on a new study published in the open-access journal Earth’s Future (published by the American Geophysical Union).
But after “decades of observations,” he says his researchers “were quite amazed how good those early projections were, especially when you think about how crude the models were back then, compared to what is available now.”
“For anyone who questions the role of humans in changing our climate, here is some of the best proof that we have understood for decades what is really happening, and that we can make credible projections….”
A new era of monitoring global sea-level change took off when satellites were launched in the early 1990s to measure the height of the ocean surface. This showed that the rate of global sea-level rise since that time has averaged about one eighth of an inch per year. Only more recently, it became possible to detect that the rate of global sea-level rise is accelerating. When NASA researchers demonstrated in October 2024 that the rate has doubled during this 30-year period, the time was right to compare this finding with projections that were made during the mid-1990s, independent of the satellite measurements.
In 1996, the Intergovernmental Panel on Climate Change published an assessment report soon after the satellite-based sea-level measurements had started. It projected that the most likely amount of global sea-level rise over the next 30 years would be almost 8 centimeters (3 inches), remarkably close to the 9 centimeters that has occurred.
But it also underestimated the role of melting ice sheets by more than 2 centimeters (about 1 inch). At the time, little was known about the role of warming ocean waters and how that could destabilize marine sectors of the Antarctic Ice Sheet from below. Ice flow from the Greenland Ice Sheet into the ocean has also been faster than foreseen.
“The findings provide confidence in model-based climate projections,” according to the paper. Again, its two key points:
- The largest disparities between projections and observations were due to underestimated dynamic mass loss of ice sheets
- Comparison of past projections with subsequent observations gives confidence in future climate projections
Thanks to Slashdot reader Mr. Dollar Ton for sharing the news.