Rapidly increasing global warming is driving a rising tide of effects that could lead to serious human suffering and ecological disaster, and there is only one way to avoid catastrophe: drastic reductions in greenhouse gas emissions.
Spanning 10,000 pages, these are the highlights of a trio of reports on climate change for August 2021, February 2022 and published on Monday. The three tomes – each with their own roster of hundreds of authors – focus on the physics, impacts and need for adaptation, and ultimately how to reduce carbon pollution.
It will be the sixth such trilogy since the Intergovernmental Panel on Climate Change (IPCC) gave its first report in 1990 and established itself as the final word on the science behind global warming.
Here are five key findings from the three reports:
No doubt
Whatever climate skeptics may say, scientific evidence has dispelled any doubt that human activity is “clearly” responsible for global warming, which has warmed the planet by an average of 1.1 degrees Celsius above pre-industrial levels. have seen.
Atmospheric concentrations of carbon dioxide – the main driver of warming, mainly emitted by burning fossil fuels – rose at least 10 times faster between 1900 and 2019 than at any other time in the past 800,000 years, and at its highest level in two million years. ,
Goodbye 1.5 °C?
The 2015 Paris Agreement calls for limiting global warming to “well below” 2 °C and, if possible, 1.5 °C. A climax of the deadly effects is already being felt and a slew of new science has prompted most countries to adopt a more ambitious aspirational goal.
But that ship may have sailed.
In each IPCC projection for a habitable future, Earth’s average surface temperature rises by about 1.5 °C, or 1.6 °C, by 2030 – a decade earlier than projections made only a few years ago.
Theoretically, it would be possible to keep temperature rise below the 1.5 °C threshold by the end of the century, but even a temporary “overshoot” could cause irreversible damage to fragile ecosystems at the poles, mountains and coastal regions. can deliver. Area.
Staying below 2°C will be a serious challenge if countries do not improve on their 2030 emissions reduction promises made under the Paris Treaty. Current national policies will heat the Earth by 3.2 °C by 2100.
avalanche of sorrow
Once a problem on the distant horizon, the devastating consequences of climate change have become a reality in the here and now. Nearly half the world’s population – between 3.3 and 3.6 billion – is “very vulnerable” to the deadly effects of global warming, which will certainly get worse.
Heatwaves so extreme that they are literally not habitable; Superstorms made more deadly by waterlogged environments and rising seas; Drought, lack of water, more disease-carrying mosquitoes and ticks.
These and other effects are set to get worse, and will disproportionately devastate Earth’s most vulnerable populations, including indigenous peoples.
Millions of people may eventually be forced out of their homes by sea levels – pushed primarily by melting ice sheets on Greenland and Antarctica – which will continue to rise over the next century no matter how quickly humanity reduces emissions.
Even if global warming is capped at 2 °C, the oceans could rise by half a meter by 2100 and two meters by 2300, more than double the IPCC estimates from 2019.
only option left
The IPCC emphasizes that it does not make recommendations, only provides background information and policy choices so that decision makers can make the right choices to ensure a “living future” for the planet and its inhabitants.
But all roads leading to a 1.5°C, or even 2°C world, involve “rapid and deep and in most cases immediate greenhouse gas emissions reductions in all sectors” – industry, transport, agriculture, including energy and cities.
Meeting those temperature targets will require drastic reductions in fossil fuel use, the IPCC says: 90 percent, 25 percent and 40 percent less coal, gas and oil, and 90 percent, 40 percent and 2100, respectively, by 2050. Up to 80 percent less.
Coal plants that do not use carbon capture technology to remove some of their pollution to generate electricity should reduce their use by 70 to 90 percent within eight years.
tipping points
The new trio of IPCC reports emphasize that never before threatens “tipping points”, temperature limits in the climate system that once exceeded can result in catastrophic and irreversible changes.
The good news is that we seem to have retreated from emissions scenarios from human sources, which could result in a 4°C or 5°C world. The bad news is that “low probability/high impact” tipping point scenarios in nature can get us there.
dissolution of ice sheets that would raise sea levels by a dozen meters or more; We are desperately trying to keep the permafrost out of the atmosphere, which is a huge storehouse of similar greenhouse gases; The transformation of the Amazon Basin from a tropical forest to a savanna – all may be triggered by additional global warming.
Where are those triggers? Scientists aren’t sure, but they do know that the risk is much greater in a world that is 2 °C warmer than 19th-century levels, which is 1.5 °C warmer.
Above 2.5 °C, the risk is “very high”.
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