Climate Letter #1568

Scientists can now describe the carbon buildup that caused the PETM (University of Birmingham).  “The PETM is the largest natural climate change event of Cenozoic time and an important yardstick for theories explaining today’s long-term increase in the average temperature of Earth’s atmosphere as an effect of human industry and agriculture.”  Global temperatures rose 4-5C during that era because of greenhouse gas emissions from volcanic lava flooding that took less than 20 thousand years to complete.  At the current rate of emissions, which is 20 to 40 times faster, we could release the same amount of carbon gases in a much shorter time span, just a few hundred years.  The warming period of the PETM, once established, lasted up to 100,000 more years before the extra carbon was taken back down by natural processes.

–The study, published by Nature Communications, is available at this site, with open access:

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An update on Australia’s bushfires, extreme heat events and drought conditions (BBC News).  “Authorities confirmed three fires had merged into a “mega blaze” north of Sydney on Friday, covering more than 300,000 hectares…..Many fires have raged for weeks, feeding off tinder-dry conditions from a severe drought which has affected much of the nation.”

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A surprising new study shows that global warming would be much worse if we had not acted to save the ozone layer in 1987 (University of New South Wales).  The same gases that were destroying the ozone layer also had a very powerful greenhouse effect, and volumes were rapidly increasing.  Their potential heating effect, on top of what we actually have, has been calculated by this group.  “New research published today in Environmental Research Letters has revealed that thanks to the Protocol, today’s global temperatures are considerably lower. And by mid-century the Earth will be – on average – at least 1°C cooler than it would have been without the agreement.”            https://www.eurekalert.org/pub_releases/2019-12/uons-hst120519.php

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Evidence points to unusual warming of ocean surfaces around Antarctica about one million years ago, which by simulation may have lead to extensive ice sheet melting (University of Otago – New Zealand).  “The simulations highlight the sensitivity of the Antarctic ice sheet to ocean warming including a minimum of 2.5m sea-level rise in the first 200 years of ocean warming.”  Atmospheric CO2 was well below the current level at that time, which is an annoying reality.  The authors propose a series of local feedbacks to account for both the very high sea surface warming and the simulated melting effect.  It’s an interesting theory, but one can wonder about how quickly it will gain acceptance.

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How much time do we have left to prevent serious climate change from happening? (Climate Home News).  The author makes an interesting argument that decarbonization must be rolling along at an advanced pace no later than 2030, otherwise we will be overcome by tending to the costly effects that will already have been established by that time.  Politically speaking, “We will certainly be dealing with climate change for longer than the next 11 years, but we may have only the next decade to prevent it.”

Carl