In 2004, if you had told James J. McCarthy that by the next presidential election every serious candidate would be talking about climate change, he wouldn’t have believed you.
Showing a slide of the multiple proposals under consideration by the 110th Congress calling for the U.S. to stabilize greenhouse gas emissions at between 450 and 550 ppm, McCarthy said on April 22 that he is amazed—and gratified—by the attention global warming is getting in Washington and elsewhere.
“In 2004, no one was talking about this,” he said. Today, Congress is paying attention, partly because “nearly 1,000 mayors and a dozen governors” are talking about global warming with their constituents, he said.
McCarthy, the Alexander Agassiz Professor of Biological Oceanography at Harvard University, presented an MIT Earth Day colloquium, “Reflections On Our Planet and Its Life: Origins and Futures,” sponsored by the MIT Energy Initiative (MITEI).
Largely as a result of our dependence on fossil fuels, Earth’s climate is changing, he said. As we look to the future, the wise use of technology and science to “decarbonize” our energy systems will give us a choice among alternative futures.
“There are multiple futures, and which of those plays out depends on choices we make,” said McCarthy, chair of the American Association for the Advancement of Science (AAAS). McCarthy has led national and international groups charged with planning and implementing studies of global change, including the Intergovernmental Panel on Climate Change (IPCC), Working Group II, which assessed impacts of and vulnerabilities to global climate change for the Third IPCC Assessment in 2001.
The first Earth Day, a 1970 college teach-in, is acknowledged as the start of the environmental movement, said MITEI Director Ernest J. Moniz. “This is a time we see unprecedented attention to clean energy and its role in addressing climate change risk mitigation,” he said.
NASA’s famous 1968 Apollo 8 photo of Earth from space led to the “realization that this really is an extraordinarily fragile planet,” McCarthy said. But no one was yet talking about global warming, even though inklings of a problem were noted more than a century earlier.
The year 1859, when physicist John Tyndall discovered that CO2 was a greenhouse gas coincidentally also marked the first commercially viable oil well in Pennsylvania and the first engine that used sparks for internal combustion of fossil fuels. Interestingly, Swedish chemist Svante Arrhenius, who was born in 1859, calculated that if CO2 doubled in the atmosphere, it would increase global temperatures by 6 degrees Celsius.
The IPCC’s latest reports show average global temperature increasing, sea levels rising, and Arctic snow cover decreasing. The past 50-plus years have seen alarming manifestations of a warmer planet such as increased flooding, droughts, and wildfires. In the northeast United States, the upper range of IPCC’s emissions scenarios would result, in three or four decades, in a Massachusetts’ summer heat index akin to South Carolina’s today.
Because of feedback within atmospheric systems, the distribution of land masses, and aerosols’ cooling influence, the Earth has not warmed uniformly, McCarthy said. Temperature rises are greatest in the Arctic, leading to record drops in Arctic ice, snow, and frozen ground.
With warming oceans and melting ice from Greenland, sea levels could rise one or two meters this century, causing coastal flooding and the reconfiguration of Arctic ecosystems. These changes could lead to the demise of Arctic subsistence cultures that will no longer be able to sustain themselves by hunting and fishing in locations that served their ancestors for hundreds of years, said McCarthy, lead author of a 2005 Arctic Climate Impact Assessment.
Without intervention, the Earth may reach temperatures by 2100 last experienced in the Eocene epoch, in which the planet heated up in one of the most rapid and extreme global warming events in geologic history, he said.
“The choices we make today will very much influence the climate for the latter half of the century,” McCarthy said. “If we go along our current path, it will be a very different climate for the rest of time.”
Fortunately, McCarthy said, the fact that global warming is finally being taken seriously may halt the downward spiral just in time. “At a moment like this, when we need extraordinary leadership, we have extraordinary leadership, not just in (President) Obama but in the team of scientists he has assembled to advise him on climate and energy,” he said. “I’m incredibly optimistic.”