In recent discussions, several friends have described why current events make them deeply pessimistic about the future. I usually respond that I’m an optimist; for example, I believe that our democratic institutions are strong enough to withstand assault from partisans who make policy through abuse of social media. What about climate change? I have to admit that it’s no longer possible to be very optimistic about our lasting impacts on Earth’s climate from continuing use of fossil fuels.
I wrote about climate change in the last chapter of my recent book, Tools for Critical Thinking in Biology, because this is the most important issue facing humanity today. After describing multiple lines of evidence about the nature of climate change, I introduced three general principles necessary for understanding future effects of climate change. These principles are inertia, feedback, and tipping points. Carbon dioxide that we add to the atmosphere today will contribute to global warming for centuries because of inertia. Various processes that affect the climate are self-reinforcing (positive feedback) or self-damping (negative feedback, see page 247 of Tools for Critical Thinking in Biology for a potential example of negative feedback in climatology). And some changes triggered by continued burning of fossil fuels will cause major changes that are irreversible for millennia; for example, melting of the Greenland ice sheet will initiate a tipping point by raising sea level up to 23 feet, changing the very geography of Earth’s continents and causing major disruption of human society.
I taught ecology for many years at the University of Nevada, Reno, and did research on beavers and other mammals. I spent about a week discussing climate change at the end of the ecology course, emphasizing the fundamental roles of inertia, feedback, and tipping points in thinking about future changes in climate caused by human activity. New research on beavers (Figure 1) by Dr. Ken Tape and colleagues at the University of Alaska provides a beautiful illustration of how positive feedback affects climate conditions. Sadly, this new research adds another reason to be pessimistic about our ability to avert the long-term effects of climate change.
On December 28, 2017, President Trump posted one of his infamous tweets: “In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming …” Eastern North America did experience a prolonged bout of unusually cold weather this winter, but climate change is about long-term trends in global conditions, not day-to-day changes in local weather. In fact, much of the Earth saw higher than average temperatures in December 2017, and the last December that was colder than the 20th century average occurred in 1985. Alaska in particular was much hotter than normal in December 2017 (Figure 2).
Much of the Arctic, including Alaska, has a thin layer of soil that freezes in winter and melts in summer and a deeper layer of permanently frozen soil, called permafrost. Dead vegetation in temperate and tropical environments decomposes, releasing greenhouse gases. In the Arctic, much dead vegetation is incorporated in permafrost, trapping organic matter that would otherwise release carbon dioxide and methane to the atmosphere. As temperatures increase, permafrost closest to the surface melts, decomposition of long-dead plant material proceeds, and these greenhouse gases are added to the atmosphere. This is a positive feedback loop because the greenhouse gases contribute to further temperature increases, leading to more melting of permafrost, leading to further temperature increases in a runaway process. It’s particularly insidious because methane is a more potent greenhouse gas that carbon dioxide.
How do beavers enter the picture? Dr. Tape’s research has not yet been published, but was summarized by Kendra Pierre-Louis in the New York Times based on a presentation by Tape at a scientific meeting in December 2017. Beavers are widely distributed in North America, but haven’t been known to occur north of the vast boreal forest that extends across much of Canada and Alaska. These far northern areas have no trees and support only low-growing plants comprising tundra vegetation. With climate change, willows and other shrubs have spread into the tundra, followed by beavers. Beavers cut these woody plants, using their bark for food and their stems and branches to build dams that create ponds where they live (Figure 2). Their hydrological engineering produces new channels for water to flow across the permafrost, causing additional melting of the permafrost and exacerbating the positive feedback process that leads to additional release of greenhouse gases. Tape and his colleagues used aerial photography and satellite imagery to document the dramatic spread of beavers in the North Slope of Alaska since 1999.
Human civilization developed during the last 11,000 years of relative climate stability. Recent temperatures on Earth have exceeded average temperatures during each of the 110 centuries in which civilization developed and flowered. We are committed to further changes in climate because of the greenhouse gases we’ve already added to the atmosphere, where they will remain for centuries (19% of the molecules of carbon dioxide emitted today by burning fossil fuels will remain in the atmosphere 1000 years from now).
Virtually all nations on Earth took a small step toward slowing the rate of climate change by agreeing to the Paris climate accord in December 2015. The United States under President Obama played a major role in facilitating this agreement. Unfortunately, President Trump gave notice of his intention to withdraw the United States from the Paris accord shortly after his inauguration as Obama’s successor in January 2017. This would make the U.S. the only nation on Earth not participating in the agreement – a true global pariah.
I used part of a tweet by President Trump to introduce Ken Tape’s new study of beavers in the Arctic. Here is the entirety of Trump’s tweet: “In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!” Trump is objecting to Obama’s commitment to the Green Climate Fund, a United Nations program to help poor countries deal with climate change. In fact, the U.S. pledged to contribute $3 billion to this fund, more than any other country in total, but far less than several other countries per capita; for example, $9.41 for the U.S. compared to $18.77 for Great Britain. Britain was fifth of 20 wealthy countries in per capita contribution to this fund and the U.S. would have been 11th, except that Trump stopped payment after $1 billion of our pledge had been delivered, leaving us at 19th out of 20.
I worry about climate change because the evidence that it’s happening is all around us – warmer temperatures, increased sea level, melting glaciers, harsher storms – and because inertia, positive feedback, and tipping points will exacerbate future changes that are already in the pipeline. It’s especially disheartening because of how quickly the U.S. has abdicated its leadership role in addressing climate change. We’ve been the most powerful nation on Earth for several decades; part of our importance on the global stage came from the example we set on issues such as environmental protection, conservation, and reliance on science for decision making. We now have national leaders who would call themselves climate skeptics but in fact are willfully ignorant of the science of climate change. By nature, I’m an optimist. Unfortunately, recent political history has turned me into a pessimist – at least about climate change.