{"id":19504,"date":"2021-08-27T10:31:05","date_gmt":"2021-08-27T14:31:05","guid":{"rendered":"http:\/\/www.cr2.cl\/eng\/?p=19504"},"modified":"2021-09-21T10:33:35","modified_gmt":"2021-09-21T13:33:35","slug":"the-4-biggest-lessons-from-the-latest-ipcc-climate-report-popular-science","status":"publish","type":"post","link":"https:\/\/www.cr2.cl\/eng\/the-4-biggest-lessons-from-the-latest-ipcc-climate-report-popular-science\/","title":{"rendered":"The 4 biggest lessons from the latest IPCC climate report (Popular Science)"},"content":{"rendered":"

The new IPCC report underscores the need for swift climate action.<\/strong><\/p>\n

By Ula Chrobak<\/p>\n

\n

The Intergovernmental Panel on Climate Change doesn\u2019t hedge in its latest assessment of the state of our planet<\/a>. \u201cIt is unequivocal that human influence has warmed the atmosphere, ocean and land,\u201d the authors write. \u201cWidespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.\u201d<\/p>\n

Climate Change 2021: the Physical Science Basis<\/em>, part of the IPCC\u2019s sixth assessment cycle, provides a thorough update to the state of climate science since the IPCC\u2019s fifth assessment in 2014. The assessment builds on the latest data to provide a snapshot of how much humans have shifted the climate since industrialization and what\u2019s in store in the future. The new report has 234 authors, references more than 14,000 scientific papers, and was subjected to review from numerous climate experts and government officials. \u201cThe most important takeaway is that climate change is now, certain, and it\u2019s here,\u201d says Diana Bernstein, a climate scientist at the University of Southern Mississippi. \u201cIf we don\u2019t address it immediately \u2026 it\u2019s going to make everybody\u2019s lives miserable.<\/p>\n

Setting a two million year record in atmospheric carbon levels<\/strong><\/p>\n

Since the Industrial Revolution, human-generated emissions of greenhouse gases, primarily carbon dioxide, have caused the surface temperature of the globe to warm by 1.1\u00baC. Just considering temperatures over land (which is less than a third of Earth\u2019s surface), the average global warming is even more\u2014about 1.6\u00baC. Each of the last four decades has been warmer than any decade preceding it dating back to 1850.<\/p>\n

Carbon dioxide is now concentrated at 410 parts per million in the atmosphere, a level that hasn\u2019t been so high since two million years ago. It is true that the planet has always had warmer and cooler fluctuations in climate, but those shifts occurred very slowly over many thousands of years\u2014glacial and interglacial cycles. The pace of warming today, on the other hand, is without parallel in the history of our species. What does that mean for us? As Laura Gallardo, coauthor of the report and climate scientist at the University of Chile, puts it: \u201cThe planet is going to survive \u2026 as long as the sun is more or less alive,\u201d she says. \u201cHowever, this short time framework in which things are changing, makes it extremely difficult for us to adapt and change in time.\u201d<\/p>\n

The window for action is nearly closed on keeping the Paris Agreement<\/strong><\/p>\n

Even if we manage to immediately cease burning fossil fuels (which is unlikely), the long-lived nature of carbon dioxide in the atmosphere means we will continue to warm the planet for a while. Global temperatures will creep upward until at least midcentury, the assessment found. That makes keeping warming within international targets like 1.5 or 2\u00baC challenging. \u201cGlobal warming of 1.5\u00b0C and 2\u00b0C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades,\u201d write the IPCC authors.<\/p>\n

Humanity\u2019s best hope is to cut emissions to net zero (with any human-caused emissions offset by some form of carbon removal) and ideally go negative. Still, even under the IPCC\u2019s \u201cvery low emissions\u201d modelled trajectory, it\u2019s estimated that temperatures will crest at 1.6\u00baC of warming by midcentury before dipping back to 1.4\u00baC by 2100. With just a temporary overshoot of 1.5\u00baC<\/a>, we can avoid crossing many dangerous climate tipping points.<\/p>\n

In developing their projections, IPCC scientists narrowed their range of \u201cclimate sensitivity,\u201d<\/a> which is how much the planet is expected to warm if the carbon dioxide concentration in the atmosphere is doubled from pre industrial levels to 560 parts per million. The likely range of warming from a doubling of CO2 is now 2.5\u00baC to 4\u00baC, with a \u201cbest estimate\u201d of 3\u00baC, narrowing from 1.5 to 4.5 \u00b0C\u2014a range that hasn\u2019t been updated since the 1970s (and the earliest estimate of climate sensitivity<\/a>, 5\u00baC, was published in 1896).<\/p>\n

Certain changes are irreversible<\/strong><\/p>\n

The extra CO2 we\u2019ve added so far is responsible for much more than a bump in global temps. Here are a few major findings from the IPCC report:<\/p>\n