Preventing an extra half-degree Celsius of heat could make a life-or-death difference in the next few decades for multitudes of people and ecosystems on this fastwarming planet, an international panel of scientists put together by the Unitd Nations reported this week.
However, the report’s authors provide little hope the world will rise to the challenge, warning that while such a goal is feasible on paper, it would require political will and vast economic transformations that are not on the near-term horizon.
The Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC) issued its gloomy report at a meeting in Incheon, South Korea, on Monday. In the 728-page document, the United Nations organisation detailed how Earth’s weather, health and ecosystems would be in better shape if the world’s leaders could somehow limit future human-caused warming to just a half-degree Celsius (0.9 degrees Fahrenheit) from now, instead of the globally agreed-upon goal of 1ºC.
The special report on global warming of 1.5ºC above preindustrial levels began as a request from the 195 nations that inked the Paris Agreement in 2015. That landmark pact called for capping the rise in global temperature to “wellbelow” 2ºC, and invited countries to submit voluntary national plans for reducing greenhouse gas emissions.
To the surprise of many – especially scientists, who had based nearly a decade of research on the assumption that 2ºC was the politically acceptable guardrail for a climate-safe world – the treaty also called for a good-faith effort to cap warming at the lower threshold.
At the same time, countries asked the IPCC to detail what a 1.5ºC world would look like, and how hard it might be to prevent a further rise in temperature.
“Unfortunately, we are already well on the way to the 1.5ºC limit, and the sustained warming trend shows no sign of relenting,” Elena Manaenkova, Deputy Secretary-General of the World Meteorological Organisation said this week.
Three years and many drafts later, the answer has come in the form of a 400-page report – grounded in an assessment of 6,000 peer-reviewed studies – that delivers a stark, double-barrelled message: 1.5ºC is enough to unleash climate mayhem, and the pathways to avoiding an even hotter world require a swift and complete transformation not just of the global economy, but of society too.
With only 1ºC of warming so far, the world has seen a climate-enhanced crescendo of deadly heatwaves, wild fires and floods, along with superstorms swollen by rising seas.
“I don’t know how you can possibly read this and find it anything other than wildly alarming,” said Peter Frumhoff, director of science and policy at the Union of Concerned Scientists, a Washington-based research and advocacy group, referring to the draft “Summary for policymakers.”
A QUESTION OF AMBITION
“For some people this is a life-or-death situation without a doubt,” said Cornell University climate scientist Natalie Mahowald, a lead author on the report.
Limiting warming to 0.5°C from now means the world can keep “a semblance” of the ecosystems we have. Adding another 0.5°C degrees on top of that — the looser global goal — essentially means a different and more challenging Earth for people and species, said another of the report’s lead authors, Ove Hoegh-Guldberg, director of the Global Change Institute at the University of Queensland, Australia.
But meeting the more ambitious goal of slightly less warming would require immediate, draconian cuts in emissions of heat-trapping gases and dramatic changes in the energy field. While the UN panel says technically that’s possible, it saw little chance of the needed adjustments happening.
In 2010, international negotiators adopted a goal of limiting warming to 2°C since pre-industrial times. It’s called the ‘two-degree goal.’ In 2015, when the nations of the world agreed to the historic Paris climate agreement, they set dual goals: 2°C and a more demanding target of 1.5°C from pre-industrial times. The 1.5°C was at the urging of vulnerable countries that called 2°C degrees a death sentence.
The world has already warmed 1°C since pre-industrial times, so the talk is really about the difference of another 0.5°C or 0.9°F from now.
“There is no definitive way to limit global temperature rise to 1.5°C above pre-industrial levels,” the UN-requested report said. More than 90 scientists wrote the report, which is based on more than 6,000 peer reviews.
“Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate,” the report states.
Deep in the report, scientists say less than two percent of 529 of their calculated possible future scenarios kept warming below the 1.5°C goal without the temperature going above that and somehow coming back down in the future.
The pledges nations made in the Paris agreement in 2015 are “clearly insufficient to limit warming to 1.5°C in any way,” one of the study’s lead authors, Joerj Roeglj of the Imperial College in London, said.
“I just don’t see the possibility of doing the one and a half” and even 2°C looks unlikely, said Appalachian State University environmental scientist Gregg Marland, who isn’t part of the UN panel but has tracked global emissions for decades for the US Energy Department.
He likened the report to an academic exercise wondering what would happen if a frog had wings.
‘UNPRECEDENTED CHANGES’
Some of the authors said they remained optimistic.
Limiting warming to the lower goal is “not impossible but will require unprecedented changes,” UN panel chief Hoesung Lee said in a press conference in which scientists repeatedly declined to spell out just how feasible that goal is. They said it is up to governments to decide whether those unprecedented changes are acted upon.
“We have a monumental task in front of us, but it is not impossible,” Mahowald said. “This is our chance to decide what the world is going to look like.”
To limit warming to the lower temperature goal, the world needs “rapid and far-reaching” changes in energy systems, land use, city and industrial design, transportation and building use, the report said. Annual carbon dioxide pollution levels that are still rising now would have to drop by about half by 2030 and then be near zero by 2050. Emissions of other greenhouse gases, such as methane, also will have to drop. Switching away rapidly from fossil fuels like coal, oil and gas to do this could be more expensive than the less ambitious goal, but it would clean the air of other pollutants. That would have the side benefit of avoiding more than 100 million premature deaths this century, the report said.
“Climate-related risks to health, livelihoods, food security, water supply, human security and economic growth are projected to increase with global warming” the report said, adding the world’s poor are more likely to get hit hardest.
Princeton University climate scientist Michael Oppenheimer said extreme weather, especially heat waves, will be deadlier if the lower goal is passed.
Meeting the tougher-to-reach goal “could result in around 420 million fewer people being frequently exposed to extreme heat waves, and about 65 million fewer people being exposed to exceptional heat waves,” the report said. The deadly heat waves that hit India and Pakistan in 2015 will become practically yearly events if the world reaches the hotter of the two goals, the report said.
Coral and other ecosystems are also at risk. The report said warmer water coral reefs “will largely disappear.”
The question now is if the report will spur governments and people to act quickly and strongly, said one of the panel’s leaders, German biologist Hans-Otto Portner. “If action is not taken, it will take the planet into an unprecedented climate future.”
Key points in the UN report on climate change
The landmark UN report on limiting global warming to 1.5º Celsius was released in South Korea this week after a-long meeting of the 195-nation Intergovernmental Panel on Climate Change (IPCC).
The “Summary for Policymakers” section of the 400-page tome underscores how quickly global warming has outstripped humanity’s attempts to tame it, and outlines stark options – all requiring a makeover of the world economy – for avoiding the worst ravages of climate change. Here are its key findings, grounded in some 6,000 peer-reviewed scientific studies:
- ‘UNPRECEDENTED CHANGES’
Capping global warming at 1.5ºC (2.7º Fahrenheit) above preindustrial levels will require “rapid, far-reaching and unprecedented changes in all aspects of society,” the IPCC said. Earth’s average surface temperature has already gone up 1ºC – enough to unleash a crescendo of deadly extreme weather – and is on track to rise another two or three degrees absent a sharp and sustained reduction in carbon pollution. At current levels of greenhouse gas emissions, we could pass the 1.5ºC marker as early as 2030, and no later than mid-century, the report finds with “high confidence.” To have at least a 50-50 chance of staying under 1.5ºC without overshooting the mark, the world must, by 2050, become “carbon neutral.” Emissions of carbon dioxide – the main greenhouse gas – should peak no later than 2020 and curve sharply downward from there, according to scenarios in the report. That’s easier said than done: humanity dumped a record amount of CO2 into the atmosphere last year.
- STEEP COST OF INACTION
The 30-page executive summary also details humanity’s “carbon budget” – the amount of CO2 we can emit and still stay under the 1.5ºC ceiling. For a two-thirds chance of success, that is about 420 billion tonnes, an allowance that would – according to current trends – be used up in a decade. The share of electricity generated by renewables – mainly hydro, solar and wind – would have to jump by mid-century from about 20 to 70 percent. The share of coal, meanwhile, would need to drop from 40 percent to low single digits. Limiting global warming to 1.5ºC will require investing about US$2.4 trillion in the global energy system every year between 2016 and 2035, or about 2.5 percent of world GDP. This price tag, however, must be weighed against the even steeper cost of inaction, the report says.
- 1.5ºC VS. 2ºC
Two degrees Celsius was long considered the temperature guardrail for a climate-safe world, but a raft of recent research shows otherwise. “Climate impacts are exponentially more dramatic when we go from 1.5ºC to 2ºC,” said Henri Waisman, a scientist at the Institute for Sustainable Development and International Relations, and a coordinating lead author of the IPCC report. What used to be once-a-century heatwaves in the northern hemisphere, for example, will become 50 percent more likely in many regions with an extra half-degree of warming. Some tropical fisheries are likely to collapse somewhere between the 1.5ºC and 2ºC benchmark. Staple food crops will decline in yield and nutritional value by an extra 10 to 15 percent. Coral reefs will mostly perish. The rate of species loss will accelerate “substantially.” Most worrying of all, perhaps, are temperature thresholds between 1.5ºC and 2ºC that could push Arctic sea ice, methane-laden permafrost, and melting polar ice sheets with enough frozen water to lift oceans by a dozen metres, past a point of no return.
- PATHWAYS
IPCC authors say the 1.5ºC goal is technically and economically feasible, but depends on political leadership to become reality. The report lays out four 1.5ºC scenarios that shadow current and future policy debates on the best way to ramp up the fight against climate change. One pathway relies heavily on a deep reduction in energy demand, while another assumes major changes in consumption habits, such as eating less meat and abandoning cars with internal combustion engines. Two others depend on sucking massive amounts of CO2 out of the air, either through large-scale reforestation, use of biofuels, or direct carbon capture.
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