The dire impact of future climate change on the US, spelt out in the federal government’s National Climate Assessment report last November, is looking even worse after the completion of further research.
Scientists involved in the assessment, an exercise mandated by Congress that takes place every four years, gave an update at the American Association for the Advancement of Science meeting in Austin.
New findings, for example about sea level rise and the frequency of severe weather, reinforced the report’s message, said Donald Wuebbles, professor of atmospheric sciences at the University of Illinois and a leader of the assessment.
“Climate change is not just something for the future. The bottom line is that our climate is changing now, extremely rapidly,” he said. “Temperatures over Europe and North America today are the highest they have been in 11,000 years”
The assessment involves hundreds of scientists in government and universities. Many were worried that it would fall foul of the Trump administration’s sceptical attitude about man-made climate change — and were relieved that no attempt was made to hold up or change the first volume of report before publication.
The second volume of the assessment, focusing on climate change’s impact on specific US regions and economic sectors, is due to appear late this year. Its preparation is proceeding smoothly without political interference, the scientists said. “So far it’s looking good,” Prof Wuebbles told the Financial Times. “They are leaving us alone.”
Two new studies show an accelerating rise in sea level as a result of both melting polar ice and thermal expansion of water as the oceans warm, said Robert Kopp, director of the Institute of Earth, Ocean and Atmospheric Sciences at Rutgers University. The sea level is rising twice as fast now as it was 25 years ago when accurate satellite measurements of the ocean surface started, he said.
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Projections for the future indicate a likely rise of between 15cm and 35cm by 2050 and between 30cm and 120cm by 2100, depending on the extent to which greenhouse gas emissions drive global warming, Prof Kopp said. “We could even get 8ft [2.4 metres] of sea level rise by 2100 in a high emissions path.”
The sea level rise that has taken place, about 20cm since 1900 and 8cm since 1993, is already causing increasingly frequent nuisance flooding along the US east coast at high tide.
Katherine Hayhoe of Texas Tech University, another lead author of the assessment, said recent research showed an alarming increase in the frequency and intensity of storms as a result of climate change. The risk of extreme rainfall such as that associated with Hurricane Harvey in Texas last August was about 1 per cent in the late 20th century and will increase to 18 per cent in the late 21st century, she said.
Prof Hayhoe concluded: “We have been smoking fossil fuels for hundreds of years. This report is an X-ray of our lungs. They are in a very serious condition.”
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