Monday, November 29

Climate crisis “unequivocally” caused by human activities, says IPCC report | Climate change


“It is unequivocal.” Those three crude words are the first in the new report from the Intergovernmental Panel on Climate Change. The climate crisis is unequivocally caused by human activities and is already unequivocally affecting every corner of the planet’s land, air and sea.

The report, produced by hundreds of the world’s leading scientists and endorsed by every government in the world, concludes that it could get a lot worse if the small chance left to avoid warming above 1.5 ° C is not immediately understood.

The scientific language of the report is cold and clear, but it cannot mask the heat and chaos that global warming is unleashing on the world. We have already caused 1 ° C of warming, getting dangerously close to the danger limit of 1.5 ° C agreed in the Paris climate agreement. Rain showers have accelerated since the 1980s.

Accelerated ice melting has dumped trillions of tons of water into the oceans, where oxygen levels are falling, suffocating the seas, and acidity is rising. The sea level has already risen 20 cm, and now there are more irreversibly baked.

Greenhouse gas emissions spewed from the burning of fossil fuels, the destruction of forests and other human activities are now clearly destabilizing the temperate climate in which civilization began, the report shows. Carbon dioxide levels in the air are now at their highest for at least 2 million years.

When was the last time we saw such a rapid warm-up? At least 2,000 years ago and probably 100,000 years ago. Temperatures that high? At least 6,500 years. Is the sea level rising so fast? At least 3,000 years. Oceans so acidic? Two million years.

All of this is already hurting people everywhere, the report explains. Heat waves and heavy rains that cause flooding have become more intense and frequent since the 1950s, affecting more than 90% of the world’s regions, according to the report. Drought is increasing in more than 90% of the regions for which there is good data. It is more than 66% likely that the number of major hurricanes and typhoons has increased since the 1970s.

So what about the future? A little warming up is already inevitable. We will definitely hit 1.5 ° C in the next two decades, whatever happens to emissions, finds the IPCC. The only good news is that maintaining that 1.5 ° C is still not impossible.

But it will require “immediate, rapid and large-scale reductions” in emissions, scientists say, of which there is no trace to date. Even reducing emissions, but more slowly, leads to 2 ° C and much more suffering for all life on Earth.

If emissions don’t decline over the next two decades, then 3 ° C of heating seems likely – a catastrophe. And if they don’t fall at all, the report says, then we’re on our way from 4C to 5C, which is apocalyptic territory.

The report is clear that there are no limits to the climate crisis. Every ton of carbon removed increases the impacts and risks of extreme heat, floods and droughts, so every ton of carbon is important. It will never be too late to act, the report shows. Instead, the real question is how bad will it get?

For example, extreme heat waves that are expected once every 50 years without any global warming are already occurring every decade. With a warming of 1.5 ° C, this will happen approximately every 5 years; with 2C, every 3.5 years; and with 4C, once every 15 months. More heating also means more interruptions to the monsoon rains that billions of people depend on for food.

More emissions also mean that the land and oceans are weakened to absorb carbon pollution, making heating even worse. With immediate rapid cuts, the natural world can still absorb 70% of our emissions. Without cuts, that comes down to just 40%.

One of the strongest sections of the report begins: “Many changes due to past and future greenhouse gas emissions are irreversible over centuries or millennia.” This particularly affects the world’s oceans and ice, which absorb 96% of global warming, which means that the ice will continue to melt and the oceans will rise towards our many crowded coastal cities.

The likely range is between 28 cm and 100 cm by the end of the century. But it could be 200 cm by then, or 500 cm by 2150, the report warns. Extreme sea level events, such as coastal flooding, which occurred only once per century in the recent past, are projected to occur at least once a year in 60% of places by 2100.

“That may seem a long way off, but there are millions of children who have already been born and who should be alive well into the 22nd century,” says Professor Jonathan Bamber of the University of Bristol, UK, and author of the report.

The many scientific advances since the last comprehensive IPCC report in 2013 mean better projections for specific regions of the world. You can’t find any safe place. For example, even at 1.5 ° C heating, heavy rains and floods are expected to intensify in Europe, North America and most parts of Africa and Asia.

“We can no longer assume that citizens of wealthier and safer countries like Canada, Germany, Japan and the US will be able to cope with the worst excesses of a rapidly destabilizing climate,” says Professor Katharine Hayhoe, chief scientist at The Nature. Conservation. “It is clear that we are all in the same boat, facing a challenge that will affect us all throughout our lives.”

The report is the sixth from the IPCC, but the first to thoroughly assess the risk of tipping points. These are abrupt and irreversible changes in crucial systems on Earth that have enormous impacts and are a growing concern for scientists. The collapse of the main Atlantic currents, the polar ice caps or the Amazon rainforest “cannot be ruled out,” the report warns.

“For the tipping points, it is clear that every extra ton of CO2 emitted today will lead to a minefield of feedback effects tomorrow,” says Professor Dave Reay, University of Edinburgh, UK.

So what can be done? The final section of the IPCC report addresses how climate change can be limited in the future. It finds that humanity has emitted 2.4 billion tons of CO2 since 1850, and that we can only filter another 400 billion tons to have a 66% chance of maintaining 1.5 ° C.

In other words, we have already spent 86% of our carbon budget, although the report says the science is clear that if emissions are reduced, temperatures will stop rising in a decade or two and increases in extreme events mortals will be very limited.

“Unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to 1.5 ° C will be beyond our reach,” says Abdalah Mokssit, secretary of the IPCC.

“But we never dictate any policy to any country, it is the governments that must make the decisions.”

Scientists have now spoken, louder and clearer than ever. Now it is up to the politicians to act.


www.theguardian.com

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