More than 200 leading scientists have warned in a report that the world faces a series of interrelated crises that threaten the existence of humans, because the sum of the effects of the crises is much greater than their individual impacts.
Climate change, extreme weather events, from hurricanes to heat waves, declining ecosystems that support life, food security and declining freshwater reserves, represent a monumental challenge for humanity in the 21st century. .
The French agency AFP details that out of 30 risks on a global scale, these five mentioned above topped the list both in terms of probability and impact, according to scientists surveyed by Future Earth, an international research organization.
Extreme heat waves, for example, accelerate global warming by releasing gases that warm the planet from natural sources, even as they intensify water crises and food shortages.
Meanwhile, the loss of biodiversity weakens the ability of natural and agricultural systems to cope with climatic extremes, which also puts the food supply at risk.
Scientists are especially concerned that rising temperatures could push the planet's climate system into a self-perpetuating spiral of global warming.
As reported by AFP, humanity is struggling, so far without success, to limit emissions of carbon dioxide (CO2) and methane, mainly due to the burning of fossil fuels.
If at the same time a warming Earth also begins to emit large amounts of these gases, for example by thawing permafrost, such efforts could be overwhelmed.
"Many scientists and policy makers are embedded in institutions that are used to thinking and acting on isolated risks, one at a time," the report said.
"We call on the world's academics, business leaders and policy makers to pay attention to these five global risks and ensure they are treated as interactive systems."
Nearly 1,000 decision makers and top CEOs highlighted the same threats in a similar survey last month before the World Economic Forum (WEF) meeting in Davos, Switzerland.
"2020 is a critical time to analyze these issues," said Amy Luers, executive director of Future Earth, saying, "Our actions in the next decade will determine our collective future."
In October, the nations of the world will come together for a major United Nations meeting in Kunming, China, to try to stop the destruction of ecosystems and the decline of biodiversity. Scientists agree that Earth is at the start of a mass extinction event, only the sixth in half a billion years, which could push a million species, or one in eight, into oblivion in the coming decades or centuries.
The next month, a critical UN climate summit, COP26, in Glasgow will reveal whether the world's major economies are willing to increase carbon reduction promises that are far short of what is needed to keep the planet hospitable to our species.
AFP reports that 2020 is also a critical year in the ongoing negotiations over the high seas, where a free fight for all in the Wild West has led to overfishing and unrestricted resource extraction.
Some scientists have begun to analyze the probability and impacts of cascading environmental crises.
Recent research has shown, for example, that some parts of the world may soon have to deal with these six extreme weather events at once, ranging from heat waves and wildfires to deluge rains and deadly storm surge.
"Human society will face the devastating combined impacts of multiple interacting climate risks," Dr. Erik Franklin, a researcher at the University of Hawaii Institute of Marine Biology and co-author of a key study in late 2018, told AFP.
"They are happening now and will continue to get worse." This is true even in optimistic emission reduction scenarios.
If, for example, humanity limits global warming to two degrees Celsius above pre-industrial levels, New York City will likely face a significant climate hazard each year, on average, by the year 2100.
The Paris Agreement on Climate Change sponsored by the United Nations in 2015 calls for keeping the temperature rise to “well below” 2.0 ° C.
However, if carbon pollution continues unabated, New York could be hit by up to four of these calamities at once, including extreme rains, sea level rise, and tsunamis. In all these scenarios, the tropical coastal areas suffer the most.