Earth is hotter than it has been in 125,000 years, but deadly heat waves, storms and floods amplified by global warming could be a preview as fossil fuels warming the planet threaten a “livable” future.
That concludes the United Nations Intergovernmental Panel on Climate Change (IPCC) that kicked off a week-long meeting to distill six historical reports totaling 10,000 pages, prepared by more than 1,000 scientists over the past six years.
Here are some of the key findings from those reports:
1.5C or 2C?
The 2015 Paris Agreement called for global warming to be kept well below 2 degrees Celsius (3.6 degrees Fahrenheit) compared to levels seen in the late 19th century.
However, a landmark 2018 IPCC report left no doubt: only the treaty’s more ambitious target limit of 1.5°C (2.7°F) can guarantee a climate-secure world. But the report warned that achieving this goal would require “unprecedented changes in all aspects of society.”
Greenhouse gas emissions must fall by 43 percent by 2030 — and 84 percent by the middle of this century — to stay within the threshold. Yet emissions have continued to rise. The world is likely to exceed the 1.5°C limit, even if it is temporary.
Every fraction of a degree counts. With a warming of 1.5°C, 14 percent of terrestrial species will be threatened with extinction. If temperatures rise by 2°C, 99 percent of warm-water coral reefs — home to a quarter of marine life — will perish and major food crops will decline.
The IPCC reports highlight as never before the danger of “tipping points” – temperature thresholds in the climate system that, once exceeded, can lead to catastrophic and irreversible changes.
The Amazon basin, for example, is already changing from tropical forest to savanna.
A warming of between 1.5°C and 2°C could push Arctic Ocean ice, methane-laden permafrost and ice sheets with enough frozen water to push the oceans several dozen meters beyond points of no return.
Avalanche of suffering
The 2022 IPCC impact report – described by UN chief Antonio Guterres as an “atlas of human suffering” – took stock of the enormous challenges facing humanity.
Between 3.3 and 3.6 billion people are “highly vulnerable” to the effects of global warming, including deadly heat waves, drought, water shortages and disease-carrying mosquitoes and ticks.
Climate change has had a negative impact on physical health globally and on mental health in regions where data are available.
By 2050, many flood-prone coastal megacities and small island nations will experience what used to be once-a-century weather disasters every year.
These and other impacts will worsen and disproportionately harm the most vulnerable populations, including indigenous peoples.
“The cumulative scientific evidence is unequivocal: Climate change poses a threat to human well-being and the health of the planet,” said last year’s IPCC impact report.
Further delays in reducing carbon pollution and preparing for impacts already in the pipeline “will miss a short and rapidly closing opportunity to secure a livable and sustainable future for all”.
Ecosystems on edge
Fortunately, forests, plants and soil absorb and store almost a third of all man-made emissions. But intensive exploitation of these natural resources also generates planet-warming CO2, methane and nitrous oxide. Agriculture consumes 70 percent of the Earth’s fresh water supply.
Oceans have kept the planet livable by absorbing a quarter of man-made CO2 and absorbing more than 90 percent of the excess heat generated by greenhouse gases.
But this has come at a cost: Seas have become acidic, potentially undermining their ability to sequester CO2, and warmer surface waters have increased the strength and reach of deadly tropical storms.
Fossil fuels: now or never
All pathways to a livable world “invoke rapid and deep and in most cases immediate reductions in greenhouse gas emissions across all sectors,” including transportation, agriculture, energy and cities, the IPCC concluded.
Meeting the Paris temperature targets will require a massive reduction in fossil fuel use, according to the IPCC.
Coal plants that do not use carbon capture technology to extract CO2 pollution must decrease by 70 to 90 percent within eight years. By 2050, the world must be climate neutral and compensate any residual emissions with removals from the atmosphere.
The world must also tackle methane (CH4), warns the IPCC. The second most important air pollutant after CO2 comes from leaks in fossil fuel production and agriculture, as well as natural sources such as wetlands.
Methane levels are the highest in at least two million years.
The good news, the IPCC stressed, is that alternatives to planet-warming fuels have become significantly cheaper. From 2010 to 2019, solar unit costs fell 85 percent, while wind energy costs fell 55 percent.
“It’s now or never if we want to limit global warming to 1.5C,” said Jim Skea, a professor at Imperial College London and co-chair of the working group behind last year’s emissions reduction report.