Changes afoot now in at least nine areas could drastically alter the Earth’s climate. There’s no time left to act on these tipping points.
LONDON, 28 November, 2019 – On the eve of a global climate summit in Madrid, seven distinguished climate scientists have issued an urgent warning of approaching planetary tipping points: within a few years, they say, humankind could enter a state of potentially catastrophic climate change on a new “hothouse” Earth.
They warn that dramatic changes to planetary stability may already be happening in nine vulnerable ecosystems. As these changes happen, they could reinforce each other and at the same time amplify planetary temperature rise, commit the oceans to inexorable sea level rise of around 10 metres, and threaten the existence of human civilisations.
Their warning is issued in a commentary in the journal Nature. Their conclusions are not – and perhaps cannot be – confirmed by direct evidence or the consensus of other scientists. They present an opinion, not a set of facts that can be scrutinised and challenged or endorsed by their peers.
And the seven researchers recognise that although such changes are happening at speed, some of the consequences of those changes will follow more slowly. Their point is that the risks of irreversible change are too great not to act – and to act now.
But the fact that they have chosen to issue such an alarm at all is a measure of the concern raised by the rapid retreat of the Arctic ice, the steady loss of the Greenland ice cap, the damage to the boreal forests, the thaw of the polar permafrost, the slowing of a great ocean current, the loss of tropical corals and the collapse of ice sheets in East and West Antarctica.
Each of these happenings – and many more – was identified more than a decade ago as a potential “tipping point”: an irreversible change that would amplify global heating and trigger a cascade of other climate changes.
“Now we see evidence that over half of them have been activated,” said Tim Lenton of the University of Exeter, UK. “The growing threat of rapid, irreversible changes means it is no longer responsible to wait and see.”
“The stability and resilience of our planet is in peril. International action – not just words – must reflect this”
The idea of a climate tipping point – a threshold beyond which dramatic climate change would be irreversible – is an old one. Two decades ago the Intergovernmental Panel on Climate Change examined the idea and proposed that, were the planet to warm by 5°C above the long-term average for most of human history, then it could tip into a new climate regime.
But in the last few decades, carbon dioxide concentrations in the atmosphere have gone from around 280 parts per million to more than 400 ppm, and global average temperatures have risen by more than 1°C. And the rate of change, driven by profligate use of fossil fuels that deposit greenhouse gases into the atmosphere, has been alarming.
“It is not only human pressures on Earth that continue rising to unprecedented levels. It is also that, as science advances, we must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming. This is what we are seeing already at 1°C global warming,” said Johan Rockström, who directs the Potsdam Institute for Climate Impact Research in Germany, and who is another signatory.
“Scientifically, this provides strong evidence for declaring a state of planetary emergency, to unleash world action that accelerates the path towards a world that can continue evolving on a stable planet.”
In 2015, at a climate summit in Paris, 195 nations promised to contain planetary heating to “well below” 2°C, and ideally to 1.5°C, by 2100. But the Nature signatories point at that even if the pledges those nations made are implemented – a “big if”, they warn – then they will ensure only that the world is committed to at least 3°C warming.
The scientists believe there is still time to act – but their dangerous tipping points are now dangerously close.
The arguments go like this. In West Antarctica, ice may already be retreating beyond the “grounding line” where ice, ocean and bedrock meet. If so, then the rest of the West Antarctic ice sheet could collapse, and sea levels could rise by three metres.
New evidence suggests the East Antarctic ice sheet could be similarly unstable, and precipitate further sea level rise of up to four metres. Hundreds of millions are already at risk from coastal flooding.
The Greenland ice sheet is melting at an accelerating rate, and once past a critical threshold could lose enough water to raise sea levels by seven metres. Even a 1.5°C warming might condemn Greenland to irreversible melting – and on present form the world could warm by 1.5°C by 2030.
“Thus we might have already committed future generations to living with sea level rises of around 10m over thousands of years. But the timescale is still under our control,” the authors warn.
They also warn that a “staggering 99% of tropical corals” could be lost if the planet heats by even 2°C – at a profound cost to both marine sea life and human economies.
They say 17% of the Amazon rainforest has been lost since 1970: a loss of somewhere between 20% and 40% could tip the entire rainforest into a destabilised state, increasingly at risk from drought and fire.
In the boreal forests of northern Asia, Europe and Canada, insect outbreaks, fire and dieback could turn some regions into sources of more carbon, rather than sinks that soak up the extra carbon dioxide.
Permafrost thaw could release ever-greater volumes of stored methane, a greenhouse gas 30 times more potent, over a century, than carbon dioxide, and so on. The dangers multiply, and each one amplifies planetary heating.
“If damaging tipping cascades can occur and a global tipping point cannot be ruled out, then this is an existential threat to civilisation,” the authors warn.
“The stability and resilience of our planet is in peril. International action – not just words – must reflect this.” – Climate News Network
Further, in 2013, Stanford’s Jonathan Koomey published a paper suggesting that instead of relying on economic cost-benefit analyses, climate policy should be shaped by “working forward toward a goal” like the Paris climate targets. In this framework, economics would be used for evaluating the most cost-effective policies to meet the targets, rather than for setting goals or arguing that all policies are too expensive so humans should instead just learn to adapt to the changing climate. A substantial amount of research has shown that approach of simple adaptation will be the costliest option of all.
Scientists Warn: Nine Climate Tipping Points Now ‘Active’ – Could Threaten the Existence of Human Civilization
By UNIVERSITY OF EXETER NOVEMBER 30, 2019
More than half of the climate tipping points identified a decade ago are now “active,” a group of leading scientists have warned.
This threatens the loss of the Amazon rainforest and the great ice sheets of Antarctica and Greenland, which are currently undergoing measurable and unprecedented changes much earlier than expected.
“We must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming.” — Johan Rockström, Potsdam Institute for Climate Impact Research
This “cascade” of changes sparked by global warming could threaten the existence of human civilizations.
Evidence is mounting that these events are more likely and more interconnected than was previously thought, leading to a possible domino effect.
In an article published in the journal Nature on November 27, 2019, the scientists call for urgent action to reduce greenhouse gas emissions to prevent key tipping points, warning of a worst-case scenario of a “hothouse,” less habitable planet.
“A decade ago we identified a suite of potential tipping points in the Earth system, now we see evidence that over half of them have been activated,” said lead author Professor Tim Lenton, director of the Global Systems Institute at the University of Exeter.
“The growing threat of rapid, irreversible changes means it is no longer responsible to wait and see. The situation is urgent and we need an emergency response.”
Co-author Johan Rockström, director of the Potsdam Institute for Climate Impact Research, said: “It is not only human pressures on Earth that continue rising to unprecedented levels.
“It is also that as science advances, we must admit that we have underestimated the risks of unleashing irreversible changes, where the planet self-amplifies global warming.
“This is what we now start seeing, already at 1°C global warming.
“Scientifically, this provides strong evidence for declaring a state of planetary emergency, to unleash world action that accelerates the path towards a world that can continue evolving on a stable planet.”
In the commentary, the authors propose a formal way to calculate a planetary emergency as risk multiplied by urgency.
Tipping point risks are now much higher than earlier estimates, while urgency relates to how fast it takes to act to reduce risk.
Exiting the fossil fuel economy is unlikely before 2050, but with temperature already at 1.1°C above pre-industrial temperature, it is likely Earth will cross the 1.5°C guardrail by 2040. The authors conclude this alone defines an emergency.
Nine active tipping points:
- Arctic sea ice
- Greenland ice sheet
- Boreal forests
- Atlantic Meridional Overturning Circulation
- Amazon rainforest
- Warm-water corals
- West Antarctic Ice Sheet
- Parts of East Antarctica
The collapse of major ice sheets on Greenland, West Antarctica and part of East Antarctica would commit the world to around 10 meters of irreversible sea-level rise.
Reducing emissions could slow this process, allowing more time for low-lying populations to move.
The rainforests, permafrost, and boreal forests are examples of biosphere tipping points that if crossed result in the release of additional greenhouse gases amplifying warming.
“Scientifically, this provides strong evidence for declaring a state of planetary emergency.” — Johan Rockström
Despite most countries having signed the Paris Agreement, pledging to keep global warming well below 2°C, current national emissions pledges — even if they are met — would lead to 3°C of warming.
Although future tipping points and the interplay between them is difficult to predict, the scientists argue: “If damaging tipping cascades can occur and a global tipping cannot be ruled out, then this is an existential threat to civilization.
“No amount of economic cost-benefit analysis is going to help us. We need to change our approach to the climate problem.”
Professor Lenton added: “We might already have crossed the threshold for a cascade of inter-related tipping points.
“However, the rate at which they progress, and therefore the risk they pose, can be reduced by cutting our emissions.”
Though global temperatures have fluctuated over millions of years, the authors say humans are now “forcing the system,” with atmospheric carbon dioxide concentration and global temperature increasing at rates that are an order of magnitude higher than at the end of the last ice age.
Reference: “Climate tipping points — too risky to bet against: The growing threat of abrupt and irreversible climate changes must compel political and economic action on emissions.” by Timothy M. Lenton, Johan Rockström, Owen Gaffney, Stefan Rahmstorf, Katherine Richardson, Will Steffen and Hans Joachim Schellnhuber, 27 November 2019, Nature.
The latest UN Climate Change Conference will take place in Madrid from December 2-13.
Climate economics researchers have often underestimated – sometimes badly underestimated – the costs of damages resulting from climate change. Those underestimates occur particularly in scenarios where Earth’s temperature warms beyond the Paris climate target of 1.5 to 2 degrees C (2.7 to 3.6 degrees F).
That’s the conclusion of a new report written by a team of climate and Earth scientists and economists from the Earth Institute at Columbia University, the Potsdam Institute for Climate Impact Research, and the Grantham Research Institute on Climate Change and the Environment. It’s a conclusion consistent with the findings of numerous recent climate economics studies.
Once temperatures warm beyond those Paris targets, the risks of triggering unprecedented climate damages grow. However, because the rate and magnitude of climate change has entered uncharted territory in human history, the temperature thresholds and severity of future climate impacts remain highly uncertain, and thus difficult to capture in climate economics models. Put simply, it’s difficult to project the economic impacts resulting from circumstances which are themselves unprecedented.
For example, if the science community does not know the temperature at which various “tipping points” might occur – things like accelerated ice sheet collapse or large carbon releases from the warming oceans or melting permafrost – then economics models will exclude the associated impacts (rapid sea-level rise or accelerated climate change).
Additionally, climate change economic cost estimates have traditionally suffered from questionable assumptions about continued economic growth, and from an inability to account for non-monetized values.
The challenges of unprecedented climate change
Research has shown that humans are warming the climate at a rate 20 to 50 times faster than some of Earth’s fastest natural climate change events. Global temperatures may already be hotter than they have been during all of human civilization, and they continue to rise rapidly.
Continuing on this rapid warming path will create a “rising probability that major thresholds in the Earth’s climate system will be breached as global mean surface temperature rises, particularly if warming exceeds 2°C above the pre-industrial level,” according to the authors of the new study. Some of these thresholds include even more severe extreme weather events (e.g. drought, heat, floods, and hurricanes), destabilizing ice sheets and the resulting sea-level rise, destruction of biodiversity, and collapsing ecosystems.
Climate models incorporate these impacts as best as they can – some better than others – but as Earth’s climate enters a state unprecedented in human history, the range and severity of damages become increasingly difficult to accurately account for. Climate economics modelers like recent Nobel Laureate William Nordhaus incorporate these climate damages into their models through what’s called the “damage function.” However, as Nordhaus has noted, “estimates of damage functions are virtually non-existent for temperature increases above 3°C. … The damage function needs to be examined carefully or re-specified in cases of higher warming or catastrophic damages.”
For example, Nordhaus’ model suggests that global warming of 6 degrees C (about 11 degrees F) – which would have catastrophic impacts on society and ecosystems – would reduce global income by only 8.5 percent. A 2010 paper led by the late economist Frank Ackerman found that not until global warming reached 19 degrees C (34 degrees F – a global temperature that is virtually incompatible with life) did the model yield a 50% reduction in economic output.
Continued economic growth: How reliable?
One problem is that these climate economic models tend to assume that the global economy will continue to grow reliably regardless of the magnitude of climate change. As climate historian Naomi Oreskes and British economist Nicholas Stern recently wrote in the New York Times, the models “approach climate damages as minor perturbations around an underlying path of economic growth, and take little account of the fundamental destruction that we might be facing because it is so outside humanity’s experience.” As Stern and economist Simon Dietz concluded in a 2015 paper, these models have “in‐built assumptions on growth, damage and risk, which together result in gross underassessment of the overall scale of the risks from unmanaged climate change.”
Numerous recent climate economics research papers have concluded that, as one might expect, continued climate change will indeed hamper economic growth. For example, that is the conclusion of
– a 2012 study led by Melissa Dell at MIT;
– a 2015 paper by Frances C. Moore and Delavane B. Diaz at Stanford;
– a 2015 study by Marshall Burke, Solomon M. Hsiang, and Edward Miguel at Stanford and Berkeley; and
– a 2018 working paper by economists at the Federal Reserve Bank of Richmond that focused on the American economy.
The 2015 study led by Burke found evidence of an optimal temperature for economic activity. Regions with average temperatures around 13 degrees C (55 degrees F, like the U.S., Japan, China, and much of Europe) have the strongest economies. As temperatures warm beyond that sweet spot, economic productivity weakens, which is especially problematic for poorer countries nearer to the equator that already have sub-optimally hot climates.
In short, economic models assuming that the global economy will continue to hum along with only relatively minor climate perturbation will inevitably underestimate the economic impacts of severe climate change. The economy has consistently grown in the past, but that doesn’t mean it must continue to grow rapidly in the future in the face of potentially extreme changes to the climate and widespread societal impacts.
Undervaluing future wellbeing and non-monetary factors
Another complication lies in what economists call the “discount rate.” Simply put, because saved money accrues interest (because of historically reliable economic growth), it’s assumed to be worth more in the future than money spent today. However, it’s easy to see where this assumption can go wrong in a world with unprecedented climate change. Saving money today rather than spending it to curb global warming could lead to severe future impacts on the economy and society. As the new report puts it, “Inappropriate discounting by economists can lead to very significant future impacts … to be treated as if they are relatively trivial compared with current impacts.”
And finally, it’s easy to forget that not everything can be evaluated based on economic costs alone. As a recent Special Report by the Intergovernmental Panel on Climate Change noted, “Many impacts, such as loss of human lives, cultural heritage, and ecosystem services are difficult to value and monetize.” A powerful hurricane might have a relatively small economic impact, but the lost lives, homes, stability, and other intangibles can carry significant non-monetary value and create trauma and suffering. For example, one study found that nearly half of low-income parents impacted by Hurricane Katrina experienced post-traumatic stress disorder.
Unless it addresses these shortcomings, economic forecasting is likely to continue to underestimate the true costs of climate change. In 2013, Stanford’s Jonathan Koomey published a paper suggesting that instead of relying on economic cost-benefit analyses, climate policy should be shaped by “working forward toward a goal” like the Paris climate targets. In this framework, economics would be used for evaluating the most cost-effective policies to meet the targets, rather than for setting goals or arguing that all policies are too expensive so humans should instead just learn to adapt to the changing climate. A substantial amount of research has shown that approach of simple adaptation will be the costliest option of all.
FILED UNDER: Dana Nuccitelli
NYTimes, Dec 2019 excerpt
cities that are quick to adapt to climate risks “are going to attract the jobs and the factories of the future,” said Eric Smith, president and chief executive officer for the Americas at Swiss Re, one of the world’s largest reinsurance companies. “There’s going to be communities that I think will be left way, way behind.”
The new research identifies 241 cities of 25,000 people or more that will require at least $10 million worth of sea walls by 2040 just to protect against a typical annual storm.
Many cities, especially small ones, will not be able to meet the costs facing them.
Those that can’t will depend on federal funding; the Trump administration is expected to soon unveil the details of two new large spending programs to fund disaster mitigation. The design of those programs could help determine which places are best able to withstand the force of climate change.
The administration is working on rules governing $16 billion in grants from the Department of Housing and Urban Development to help cities and states protect themselves against the effects of future natural disasters, the largest such award ever made by the department. The Federal Emergency Management Agency is also currently preparing rules for grants to pay for climate-resilient infrastructure.
A FEMA spokeswoman, Abigail Dennis, said the agency is asking governments, businesses, academics and “vulnerable and at-risk populations” to provide input on the design of its new grant program, called Building Resilient Infrastructure and Communities.
“The increasing frequency, impact and cost of disasters demands that we invest in mitigation and reduce disaster suffering,” Ms. Dennis said by email. The program “will support measures to reduce the vulnerability of communities and public infrastructure before a disaster strikes.”
But even that funding is likely to fall far short of the vast need. So experts have proposed ways of focusing federal money where it can do the most good — even if that means some places are left out.
One approach would be for the federal government to spend the money based simply on where it would most reduce the future cost of damages, according to Craig Fugate, who ran FEMA during the Obama administration.
“The way I would do it is, how much risk avoidance do I get for every dollar I invest?” Mr. Fugate said.
He acknowledged that Congress would probably object to that approach, since it would likely mean FEMA would concentrate its resilient-infrastructure funds in just a handful of states.
“Which then immediately runs into, ‘Well, what about my state?’,” Mr. Fugate said. “My sense is, knowing how the Senate works, they’re going to have to give every state something.”
Another option would be for the federal government to distribute climate protection money based on a city’s property value, its historical and cultural importance, and how much it contributes to the national economy, said Harriet Tregoning, who was in charge of the housing department’s Office of Community Planning and Development during the Obama administration.
Cities could increase their chances of getting money by reducing their exposure to disasters, perhaps by retrofitting their buildings, implementing aggressive building codes and zoning restrictions, and helping residents leave the most vulnerable neighborhoods, Ms. Tregoning said. And there could be extra points for cities that take in people forced to flee other parts of the country.
A city seeking federal money for climate protection should “do everything within its power to make that investment worthwhile,” Ms. Tregoning said.
Many experts believe that there are hard choices ahead.
Robert S. Young, director of the Program for the Study of Developed Shorelines at Western Carolina University, said Congress should appoint a group of technical experts to decide which coastal communities the federal government should protect.
That decision would depend on which places are most important, and also which are easiest to defend. Congress would then vote to accept or reject the list, similar to the process for deciding which military bases to close.
“We cannot protect all of those places where they are,” Mr. Young said. “We should choose the places that are most sustainable.”
He acknowledged that the odds of Congress taking such an approach weren’t high, at least not yet.
“To be able to sensibly make these kinds of decisions in an organized fashion, using data?” Mr. Young said. “That’s a gigantic assumption, in my opinion.”
Mr. Smith, of Swiss Re, said that cities should take responsibility for protecting themselves from the rising toll of disasters, rather than waiting for the federal government.
In his view, the chief obstacle is the refusal by some local officials to acknowledge what is happening.
“The challenge is, we’re fighting about whether or not there’s climate change,” Mr. Smith said. “They don’t want to embrace what’s right in front of us.”
For more news on climate and the environment, follow @NYTClimate on Twitter.
Christopher Flavelle covers climate adaptation, focusing on how people, governments and businesses respond to the effects of global warming. @cflavA version of this article appears in print on June 22, 2019, Section A, Page 14 of the New York edition with the headline: Many Cities Under Threat, but How Many of Them Can Be Protected?. Order Reprints | Today’s Paper | SubscribeREA