Earth has not been so warm since the Pliocene Epoch roughly 3 million years ago
Among the many things that IPCC report released on Monday had said very categorically, one of utmost significance is that the world is running out of time. Climate change is already affecting every inhabited region across the globe with human influence contributing to many observed changes in weather and climate extremes.
If the world drastically cuts emissions in the next decade, average temperatures could still rise 1.5C by 2040 and possibly 1.6C by 2060 before stabilizing.
If the world does not cut emissions dramatically and instead continues the current trajectory, the planet could see 2.0C warming by 2060 and 2.7C by the century’s end.
The earth has not been that warm since the Pliocene Epoch roughly 3 million years ago — when the first ancestors to humans were appearing and oceans were 25 meters (82 feet) higher than today.
See, what the report says,
“Global mean sea level has risen faster since 1900 than over any preceding century in at least the last 3000 years. The global ocean has warmed faster over the past century than since the end of the last deglacial transition (around 11,000 years ago). A long-term increase in surface open ocean pH occurred over the past 50 million years, and surface open ocean pH as low as recent decades is unusual in the last 2 million years.”
It could get even worse, if warming triggers feedback loops that release even more climate-warming carbon emissions — such as the melting of Arctic permafrost or the dieback of global forests. Under these high-emissions scenarios, Earth could broil at temperatures 4.4C above the preindustrial average by 2081-2100.
Emissions “unequivocally caused by human activities” have pushed today’s average global temperature 1.1C higher than the preindustrial average — and would have pushed it 0.5C further if not for the tempering effect of pollution in the atmosphere, the report says.
That means that, as societies transition away from fossil fuels, much of the aerosols in the air would vanish — and temperatures could spike.
Scientists warn that warming more than 1.5C above the preindustrial average could trigger runaway climate change with catastrophic impacts, such as heat so intense that crops fail or people die just from being outdoors.
Every additional 0.5C of warming will also boost the intensity and frequency of heat extremes and heavy rainfall, as well as droughts in some regions. Because temperatures fluctuate from year to year, scientists measure climate warming in terms of 20-year averages.
The 1.1C warming already recorded has been enough to unleash disastrous weather. This year, heat waves killed hundreds in the Pacific Northwest and smashed records around the world. Wildfires fueled by heat and drought are sweeping away entire towns in the U.S. West, releasing record emissions from Siberian forests, and driving Greeks to flee their lands by ferry.
Continued global warming is projected to further intensify the global water cycle, including its variability, global monsoon precipitation and the severity of wet and dry events. Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.
Greenland’s ice sheet is “virtually certain” to continue melting. Oceans will keep warming, with surface levels rising for centuries to come.
Glaciers are melting and receding across the globe, including in the Himalayas, and that this is now a phenomenon that is “locked in’” and cannot be reversed. It adds that the level of temperature rise in the mountains and glacial melt is unprecedented in 2,000 years.
It is also virtually certain that the snow cover will decline over most land regions during the 21st century, in terms of water equivalent, extent and annual duration.
It’s too late to prevent these particular changes. The best the world can do is to slow them down so that countries have more time to prepare and adapt.
But even to slow climate change, the report says, the world is running out of time.
As three-time IPCC co-author Sonia Seneviratne, a climate scientist at ETH Zurich sums it up, “We have all the evidence we need to show we are in a climate crisis.” She is not sure if she will sign up for a fourth report. She says, “Policy makers have enough information. You can ask: Is it a meaningful use of scientists’ time, if nothing is being done?“