This post is a part of a series on Ask a Scientist
The immediate threat of the coronavirus pandemic has galvanized international attention, but the long-term threat posed by the climate crisis remains on many people’s minds. We all realize that after the world recovers from this novel virus, we will still have to address the enormous threat posed by climate change.
UCS recently received a question from one of our members who, like many, is thinking ahead. “2030 is often cited as the year when climate changes become irreversible,” Raymond K. from North Attleboro, Massachusetts, asks. “What is the real significance of 2030?”
That date began drawing more attention two years ago and, unfortunately, it has been confusing. Headlines at the time warned that “We have 12 years to limit climate change catastrophe,” “Planet has only until 2030 to stem catastrophic climate change,” and “The world has just over a decade to get climate change under control.”
To set the record straight about what scientists are telling us and what the world has to do in the next decade to avoid the worst possible consequences of a warming world, I turned to Dr. Brenda Ekwurzel, director of climate science for our Climate and Energy Program. Ekwurzel is a coauthor of the Fourth National Climate Assessment Volume II, which was published in 2018.
EN: Thanks for helping us get a handle on what this warning about 2030 is all about. Where did the idea come from that we have until the end of this decade to drastically cut carbon emissions or the planet is cooked? What does it mean?
BE: It is easy to see how those headlines can be confusing. Let me demonstrate why by describing an everyday experience of baking dinner. You would start by turning the oven dial to the desired temperature, wait until the ding signals that the oven has reached that temperature, and then put your dinner in.
The headlines you cited describe the approximate time it would take, at the 2017 global emissions rate, to accumulate emissions that “dial in” a specific temperature. The international Paris climate agreement set the desired global average temperature to be 1.5 degrees Celsius (°C). It was accompanied by a stern warning from scientists to not exceed 2°C above pre-industrial levels.
Based on complex interactions and timing, the UN Intergovernmental Panel on Climate Change’s special report on 1.5°C—which it published in 2018—calculated the relative chances for staying below 1.5°C Celsius given how much greenhouse gases the world continues to emit. The more the world emits, the IPCC said, the lower the chance of meeting the desired temperature. For a decent chance—67 percent probability of meeting that average temperature target—we can set the emissions “oven dial” to a cumulative 420 gigatonnes of equivalent carbon dioxide, for reasonable chance—50 percent probability—to 580, and for a low chance—33 percent probability—to 840. Given the uncertainties associated with permafrost thawing and wetlands releasing carbon, methane and other non-carbon dioxide emissions, climate feedback responses to all emissions, and historic warming, most climate scientists recommend the most stringent carbon budget as the prudent choice.
OK, so let’s set the cumulative emissions budget dial to the prudent choice of 420 gigatonnes of equivalent carbon dioxide. If we assume the 2017 global emissions of around 42 gigatonnes of equivalent carbon dioxide continued, then we would have 10 more years before the average global temperature dial would be set to 1.5°C. The IPCC special report said this remaining budget starts on the first of January 2018, which means by the end of 2027 the world would have used up the 67 percent chance budget at that rate.
That’s what those headlines you cited were referencing—the idea that we have little time left to meet the Paris agreement temperature limit. What is slightly confusing is the world’s average temperature would not immediately rise to 1.5°C above preindustrial levels. Climate scientists have studied the time it takes for interactions among the earth, ocean, cryosphere, atmosphere and biosphere to estimate the time lag before the world reaches that temperature — just like an oven’s preheat time.
EN: Where are we now, two years after the IPCC concluded that carbon emissions would have to start dropping “well before 2030” and be on a path to declining some 45 percent below 2010 levels by that year? Are the signatories to the Paris agreement on the way to meeting their targets and, equally important, are their targets ambitious enough to get them to net zero emissions by midcentury?
BE: According to the Global Carbon Project, the fossil fuel sector’s global carbon emissions increased in 2019. Most scientists who keep track of country emissions say there’s an emissions gap between the Paris climate agreement and country emissions pledges that will put us closer to a 3°C world than a 2°C world. Governments have to do much more to enact policies in line with Paris agreement goals.
The bigger point is, however fast or slow the world burns through the carbon budget for 1.5°C, from that moment onward the world would have to remove the equivalent of all the global warming emissions released every year to stay below 1.5°C. The higher the cumulative emissions, the quicker we surpass the “prudent” budget and make it much more difficult to stay below the 1.5°C temperature limit.
If the world started reducing emissions now, there would be more time to reach the 1. 5°C limit. That would make it more likely we could implement measures to reach net zero emissions no later than 2050 and then begin to remove more carbon than the amount we emit from that point going forward. We’re talking about net negative emissions. That’s a tall order.
EN: What would likely happen if industrialized nations do not reach net zero carbon emissions by 2050? For example, what would the U.S. climate look like? And although there is no apparent link between climate change and the coronavirus, wouldn’t the kind of changes scientists foresee make it more likely that some diseases will become more widespread?
BE: We already see how dangerous a 1°C warmer world of today is, where climate change has made extreme weather events much more severe. These events will only get worse with a 1.5°C increase. According to the IPCC special report on 1.5°C, 70 to 90 percent of warm water coral reefs would likely die, and, with a 2°C increase, food availability in southern and northern Africa, the Amazon, central Europe, and the Mediterranean would be further reduced.
Obviously, the United States also would suffer damages. You asked about how a warming climate could increase the incidence of disease. The Fourth National Climate Assessment, which I worked on, offers some stark examples. For one, the mosquito that transmits West Nile virus and the tick that transmits Lyme disease would trigger higher rates of infection in the Midwest.
The good news is that constraining the global temperature increase to 1.5°C could limit direct damages to the U.S. gross domestic product to 1 percent or less. Surpassing that threshold, on the other hand, would mean ever more damage to public health and our economy.
EN: What are the main actions countries will have to take to maintain a livable planet? Do we have the necessary technology today to get the job done?
BE: The IPCC special report assessed with “very high confidence” that the world has the technological and societal know-how to meet the 1.5°C target. But the IPCC also warned with high confidence that if not managed carefully, some of the strategies employed to accomplish that goal could exacerbate poverty by undercutting access to food, water and energy for disadvantaged communities around the world.
So what do nations around the world need to do—especially the United States and other countries that are primarily responsible for climate change? UCS has identified five interconnected steps.
First, motors, appliances, infrastructure, industrial processes and all modes of transportation have to become more efficient. Some sectors of our economy are out front on this. For example, architects, engineers, material scientists and historic preservation experts, to name just a few, are working together to ensure that buildings are renovated to dramatically cut energy consumption and carbon emissions.
Second, we need to “decarbonize” electricity generation by transitioning from coal and natural gas to low- and no-carbon sources, especially wind, solar, and geothermal. We also have to invest in energy storage, modernize our outmoded transmission grid, and capture and store carbon emissions that the electricity sector continues to release.
Third, we have to “electrify” just about everything. We need to transform our transportation sector by transitioning to electric vehicles of all sizes, from two-door passenger cars to buses, big rig trucks and trains. We have to heat and cool our buildings with low- and no-carbon electricity. And nearly all of our industrial processes will have to capture carbon or run on zero-carbon electricity.
Fourth, we will have to suck carbon out of the atmosphere naturally—by planting trillions of trees, for example—and with technology. At this point we have expensive prototypes that can do that, but it will take some technological breakthroughs to accomplish that goal at the scale we need.
Finally, we will have to dramatically reduce methane and other planet-warming gases besides carbon dioxide. Wetlands, ruminant animals—cows and sheep—and natural gas leaks release methane, which traps more heat than carbon dioxide and after around a decade it converts to carbon dioxide. Meanwhile, nitrous oxide, which is largely a byproduct of farming practices and soil, can trap heat for more than a century.
I know we are now preoccupied with protecting our families and communities from the coronavirus pandemic, and rightly so. As the epidemic eases—and hopefully it will sooner than later—we will be faced with rebuilding the economy and putting people back to work. It is critical that we take steps to rebuild the economy in a way that increases our health and resilience in the face of climate change. Investing in the five-step program I just outlined has a huge potential to generate new jobs and can put us on the path to avoid the worst consequences of a warming world.
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