Tipping Point Analysis
The world could hit a tipping point that causes warming to spiral out of control — a scenario scientists call 'Hothouse Earth.' The Earth could cross a sort of tipping point that would trigger further warming. Humans have changed the world's climate systems by emitting carbon dioxide and other greenhouse gases.
According to a new paper, humans could warm the world so much that we'd cause the planet's natural climate systems to trigger further warming — a scenario called "Hothouse Earth." In that world, the average temperature could rise 4 or 5 degrees Celsius more than it already has, leading to extreme heat and up to 200 feet of sea-level rise.
Our ability to keep Earth habitable may be more limited than we realize.
Human activity could push the planet over a number of tipping points that would cause global temperatures to rise even higher than we've driven them already, according to a new paper published in the journal Proceedings of the National Academy of Sciences.
The research suggests that certain natural systems on the planet could be activated by warming and consequently trigger further warming. In that situation, Earth's average temperature might reach 4 or 5 degrees Celsius above pre-industrial temperatures. (For context, the goal of the Paris agreement was to prevent temperatures from rising more than 2 degrees C.) The paper's authors refer to this scenario as "Hothouse Earth." "These tipping elements can potentially act like a row of dominoes," Johan Rockström, a co-author of the paper and the executive director of the Stockholm Resilience Centre, said in a news release. "Once one is pushed over, it pushes Earth towards another. It may be very difficult or impossible to stop the whole row of dominoes from tumbling over. Places on Earth will become uninhabitable if 'Hothouse Earth' becomes the reality." If this were to happen, the world would become far warmer than it's been for at least the past 1.2 million years. Sea levels around the globe would likely rise between 33 and 200 feet higher than they are now.
We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values. Similar Articles Science and Culture: Imagining a climate-change future, without the dystopia Collapse of a desert bird community over the past century driven by climate change Climate change and educational attainment in the global tropics Science and Culture: Can climate change games boost public understanding? Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change See more
Refugees in Yemen collect water under strict rationing due in part to drought. A new IPCC report finds that events like these will become more frequent and devastating under 2ºC of warming compared to 1.5ºC. Refugees in Yemen collect water under strict rationing due in part to drought. The new IPCC report finds that events like droughts will become more frequent and devastating under 2ºC of warming compared to 1.5ºC. Giles Clarke/UN OCHA/Getty Images We have just 12 years to make massive and unprecedented changes to global energy infrastructure to limit global warming to moderate levels, the United Nation’s climate science body said in a monumental new report released Sunday. “There is no documented historic precedent” for the action needed at this moment, the Intergovernmental Panel on Climate Change (IPCC) wrote in its 700-page report on the impacts of global warming of 2.7 degrees Fahrenheit, or 1.5 degrees Celsius. From rising sea levels to more devastating droughts to more damaging storms, the report makes brutally clear that warming will make the world worse for us in the forms of famine, disease, economic tolls, and refugee crises. And there is a vast gulf between the devastation from 1.5°C, what’s considered the moderate level of average warming, and 2°C. “It’s very clear that half a degree matters,” said Valérie Masson-Delmotte, co-chair of IPCC Working Group I at a press conference in Incheon, South Korea, where the report was released. Under the Paris climate agreement, nations set a goal of limiting warming to 3.6°F, or 2 °C, increase in global average temperatures, with ambitions of a stricter limit of 2.7°F, or 1.5°C of warming. The UN asked the IPCC to figure out what it would take to hit the 1.5°C target, and what’s in store for the world if we did pull it off. The team pooled more than 6,000 scientific publications, drew contributions from 133 authors, and had more than 1,000 scientists review the findings. As expected, the report doesn’t pull any punches: Staying at or below 1.5°C requires slashing global greenhouse gas emissions 45 percent below 2010 levels by 2030 and reaching net zero by 2050. Meeting this goal demands extraordinary transitions in transportation; in energy, land, and building infrastructure; and in industrial systems. It means reducing our current coal consumption by one-third. It also demands a vast scale-up of emerging technologies, such as those that remove carbon dioxide directly from the air. All in the very narrow window of the next 12 years while our momentum pushes us in the wrong direction. View image on Twitter View image on Twitter Fatih Birol ✔ @IEABirol We expect energy-related CO2 emissions will increase once again in 2018 after growing in 2017 140 6:44 AM - Oct 8, 2018 205 people are talking about this Twitter Ads info and privacy The report also shows there’s no avoiding the costs of climate change; we either invest now to clamp down on greenhouse gases, or we pay down the line through property damage and lost lives. The additional sea level rise of going from 1.5°C to 2°C would put another 10 million people at risk, for example. Another key finding is that every bit of warming matters, so every fraction of a degree we can knock off the global thermostat will pay dividends across economies. In short, things will get worse. We can avoid some of the worst-case-scenarios of global warming, but the easiest options are no longer on the table. Regardless, our action or inaction both stand to shape the future of our planet. We still have a shot at limiting warming to 1.5°C, but time is running out As far as the science goes, there isn’t much new here. Anyone who’s been following climate research over the past six years since the last major IPCC report came out in 2012 will find much of the conclusions familiar. And that’s typical. IPCC reports pool together research that’s already been published to paint a picture of how the world will change as it heats up. Since the early 19th century, humans have pumped increasing amounts of heat-trapping gases into the atmosphere, a consequence of burning fossil fuels to drive industry. We now spew carbon dioxide, the main human-produced greenhouse gas, at a rate of 2.4 million pounds per second. The new IPCC report emphasizes that the 1 degree C of global warming since the dawn of the industrial revolution is already wreaking havoc through more damaging extreme weather and rising oceans. However, further warming depends on more greenhouse gas emissions, according to the report (emphasis added): Warming from anthropogenic emissions from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise, with associated impacts (high confidence), but these emissions alone are unlikely to cause global warming of 1.5°C. What this means is that we still have a chance to limit a very significant amount of warming this century. However, hitting the 1.5°C target leaves just 0.5°C of headroom over the next 80 years. That demands getting to net-zero greenhouse gas emissions by the middle of the century, which in turn requires an almost immediate, precipitous decline in emissions: Greenhouse gas emissions have to fall rapidly in order to limit global warming to 1.5 degrees Celsius. Greenhouse gas emissions have to fall rapidly in order to limit global warming to 1.5 degrees Celsius. IPCC So when it comes to greenhouse gas emissions, we can’t just take our foot off the accelerator; we have to slam on the brakes. The half degree between and 1.5°C may not seem like much, but it’s a yawning gap in terms of the effort required and the consequences thereof. Remember, we’re talking about a global average, which means a change over every part of the world. The amount of energy needed to heat the whole planet by 0.5°C is immense. So is the effort to avoid it. There’s no way to hit the 1.5°C target without removing carbon dioxide from the air Cutting greenhouse gas emissions sharply enough to reach the more ambitious climate mitigation goal requires a massive global shift in energy use. The pathways outlined in the report aren’t counting on any magical technologies that don’t yet exist; the greenhouse gas mitigation pathways use systems we have now. But they do require deploying them at massive, unprecedented scales. In particular, the 1.5°C goal will require sucking carbon dioxide out of the air, even if the planet doesn’t overshoot its carbon budget. For greenhouse gas sources like commercial shipping or from agriculture, there may not be any feasible way to trap their emissions, so the only option of balancing out that carbon is to pull it back from the atmosphere. That’s why countries need to start thinking about negative greenhouse gas emissions — there’s no way around it. “We have not identified any pathways that get to 1.5°C without carbon dioxide removal,” said Jim Skea, co-chair of IPCC Working Group III, at the Incheon press conference. Carbon dioxide removal can take the form of direct air capture, where machines scrub carbon dioxide from the air. It can also come from using bioenergy with carbon capture and sequestration, where plants pull carbon dioxide from the air and scrubbers prevent the carbon from the resulting biofuels from reaching the sky. Land use, from how we graze cattle to how we plant forests, is also a critical tactic for removing carbon dioxide from the atmosphere. But how much removal we need depends on what other tactics we use, whether that’s energy efficiency, switching to low-carbon energy sources, or cutting our energy use overall. In the worst-case scenario, we may have to drawdown upward 1,000 gigatons of carbon dioxide from the atmosphere by 2100, a massive international undertaking. An avocado grove affected by a major dought in California’s Central Valley in 2014. Droughts and crop failures will become more frequent as global warming increases. Getty Images Everything we do matters for the global climate, which in turn matters for us One point the authors repeatedly emphasize in the IPCC report is that the impacts of climate change get worse as temperatures go up. It seems like an obvious point, but researchers have substantiated it. Extreme heat and storms, as well as related outcomes like disease and poverty are projected to rise with temperatures. “Climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5°C and increase further with 2°C,” according to the report. But the inverse also holds true; avoiding warming also yields direct and indirect gains for societies. “Improved air quality resulting from projected reductions in many non-CO2 emissions provide direct and immediate population health benefits in all 1.5°C model pathways,” authors wrote. “Every extra bit of warming makes a difference,” said Hans-Otto Pörtner, co-char of IPCC Working Group II, at the press conference. The question now is how seriously governments will take these findings. If past climate reports are any indication, odds are it will receive some lip-service but little action. The number of new coal plants in the world is declining, for example, but that still means new coal plants are coming online and these generators will emit carbon dioxide for decades. The IPCC researchers will present their findings at the Katowice Climate Change Conference in Poland in December. 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