To have the best chance of avoiding the worst impacts of climate change, the world needs to limit global warming to 1.5 degrees Celsius–and to do that, society needs to completely transform over the next three decades, according to a new report from the UN’s Intergovernmental Panel on Climate Change. Global CO2 emissions may need to peak around 2020. By midcentury, we have to reach net zero emissions.
The report explains why it’s so important that we meet the 1.5 degree target, and how difficult that will be to accomplish. The changes required, from energy to agriculture, are “unprecedented in terms of scale,” the group writes in a summary for policymakers. And right now, we’re not anywhere close to the path to make it happen.
“The reality is that we’re very off track from where we need to be,” says Rachel Cleetus, policy director for the Climate and Energy Program at the nonprofit Union of Concerned Scientists, who was not involved with the new report. If our current emissions rates hold, we’ll reach 1.5 degrees C of warming by 2030.
If every country fulfills the pledges it made for the Paris agreement in 2015, the world may still warm 2.6 to 3.2 degrees C by the end of the century, by some estimates. The Paris agreement committed to limit warming to well below 2 degrees, and pursue the even harder goal to limit it to 1.5 degrees. The new report explains why going that far is critical, based on a summary of recent research that shows that the impacts at 2 degrees are much worse than previously understood.
“There are material differences between 1.5 C and 2 C,” says Cleetus. “This points out that every fraction of a degree really does matter.”
By the end of the century, if warming stops at 1.5 degrees, the sea level rise may be nearly four inches lower than if it stops at 2 degrees. That slower rate of rising water would mean that people living in island nations and along coastlines would have more time to adapt. As many as 10 million fewer people would be exposed to risks like flooding.
At 1.5 degrees of warming instead of 2 degrees, there would be a lower risk of extreme hot days that can lead to deaths. “We know that the risk of extreme heat has already gone up as a result of the 1 degree of global warming that’s already happened,” says Noah Diffenbaugh, a geoscientist and senior fellow at Stanford Woods Institute. “So we can expect further increases in that risk at 1.5 degrees. But the increase is substantially curbed at 1.5 compared with the 2-degree target.”
Areas like sub-Saharan Africa and the Mediterranean would still suffer from droughts, but farms would be able to grow more food than they could with 2 degrees of warming. The proportion of people around the world exposed to water stress could be cut in half. The risk to fisheries would be lower. Coral reefs would have a chance to survive. A huge percentage of reefs, from 70-90%, could still be lost with 1.5 degrees of warming. But if warming stops at 2 degrees, more than 99% of reefs could disappear. At 1.5 degrees, fewer species would go extinct. Fewer ecosystems would be irreversibly lost.
Limiting warming to 1.5 degrees would also give the world a better chance of avoiding major tipping points like the collapse of the West Antarctic Ice Sheet. It could prevent as many as 2.5 million square kilometers of permafrost from melting over the long term.
The transition necessary to meet the 1.5-degree target is almost unimaginably huge, and will require large investments. But Diffenbaugh’s research has found that, relative to the eventual economic damage of not acting aggressively enough to protect the planet in the future, it would cost much less to make changes now. “It’s potentially trillions of dollars in economic benefits from avoiding damages,” he says. One recent report calculated the benefits at $26 trillion.
The world needs to make decisions now for the future. Trillions of dollars will soon be invested in new infrastructure; if we make the wrong choices, they’ll be locked in, according to the same recent report. We need to make to make major changes in transportation, buildings, industry, and how we use land. We also will need to rely on carbon removal–whether that’s as low-tech as planting trees or using new technology like direct air capture that can suck CO2 from the atmosphere. The longer we wait to act, the IPCC report says, the more we’ll have to use this type of technology, which has never been proven at a large scale.
Another recent report from the consulting firm PwC makes it clear that even limiting warming to 2 degrees C will be a stretch: “There seems to be almost zero chance of limiting warming to well below two degrees (the main goal of the Paris Agreement), though widespread use of carbon capture and storage technologies, including Natural Climate Solutions, may make this possible,” it says. “Each year that the global economy fails to decarbonize at the required rate, the two-degree goal becomes more difficult to achieve.”
Still, Cleetus says that we have most of the technology we need to make the change. “We have a lot of the solutions available to us today,” she says. “There’s certainly things that we’ll need to invest in more to develop the next generation of solutions. But I would say the biggest obstacle really is political will.”
When governments made pledges for the Paris agreement, they knew those pledges would have to get much more ambitious–and the time for that to happen is now. When the next climate talks happen this December, the new report is designed to give governments the incentive to go much further, faster.
The risk that we miss the 1.5-degree target is very real. But it’s still possible that it can be achieved. The beginnings of change are underway, from plans to ban the sale of gas and diesel cars in countries like France and India to corporations shifting to 100% renewable electricity. In the U.S., after Trump pulled out of the Paris agreement, cities, states and businesses will need to step up even more than they already have to ensure a chance of meeting the goal. Changes in individual behavior–such as eating less meat and driving less–also matter.
“We have to step up and show the global community that we’re still going to live out to the goals of the Paris agreement and we understand that it’s in our best interest to do so,” says Cleetus. “We have an election coming up on November 6th. Folks should factor climate change into how they vote. Climate action matters, and our policymakers need to hear that. We will hold them accountable on this issue.”