Last month, the Intergovernmental Panel on Climate Change (IPCC)—a United Nations group that has been examining the state of the climate and climate science since 1988—released its fifth assessment, which included the report, “Climate Change 2014: Mitigation of Climate Change.” The report, which stresses the need for immediate action, offers disturbing predictions that come as no great surprise to Irina Marinov. Marinov, an assistant professor of earth and environmental science, is a climate modeler who works on understanding the role of the oceans in regulating atmospheric carbon dioxide (CO2) and the global climate.
Marinov observes everything from climate-driven changes in deep ocean currents and temperature to nutrient cycling to ocean biology. Her work has helped demonstrate the important role of phytoplankton in regulating atmospheric greenhouse gases. These invisible plants take up CO2 at the surface of the ocean, then decompose back into CO2 and nutrients. “If we put four particles of CO2 into the atmosphere, one will end up in these ocean plants and make its way in the deeper ocean” says Marinov. “We don’t think of the climatic role of phytoplankton when we swim in the ocean, because we can’t see them, but these microscopic ocean plants photosynthesize just as much as land plants.”
When the planet warms, the hydrological cycle intensifies, producing extra precipitation in the North Atlantic and polar Southern Ocean. This means that surface ocean water becomes less salty, which makes it sink less. Recent work by Marinov’s group and collaborators at McGill University shows that as a consequence, there will be less formation of deep water in high latitude oceans, with carbon footprint implications.
Without the ocean, warming of the planet would be much faster than what we are currently observing. Understanding the ocean’s role in the carbon cycle is crucial. “Luckily for us, the ocean has a very slow circulation timescale, unlike the atmosphere, which mixes gases like CO2 within a year,” says Marinov. “In the ocean, you have thousand-year timescales, which means ideas of ocean geoengineering—developing ways of getting rid of atmospheric CO2 by manipulating natural processes to store more in the ocean—are still a potential mechanism of dealing with greenhouse gases.”
Geoengineering ideas are not limited to the ocean. Some, like solar radiation management, target the atmosphere. “This method involves using huge white panels to reflect incoming solar radiation, which in turn cools the planet. You can even inject sulfate into clouds, which makes them more reflective,” Marinov notes. Downsides of such geoengineering ideas, such as changes in the local precipitation patterns, have yet to be properly assessed.
In addition to summarizing the climate science up to date, the IPCC report contains a “Summaries for Policymakers” section to aid in the legislative process. Since the Kyoto Protocol of 1997, carbon emissions have leveled off or decreased among developed nations. By contrast, in developing countries with rapid urbanization, like China and India, there has been a steep recent increase in emissions. But, as Marinov notes, the politics of climate change is nontrivial, as each country interprets differently the emission data. “These developing nations are arguing that they should not pay a climate warming ‘fee’ because they had much lower levels of carbon emissions in the past, before the mass urbanization and Asian economic boom. There are even arguments that the developed countries are actually playing a large role in their increase in emissions because of the recent outsourcing of industries.”
While the vast majority of nations on a global scale have accepted the IPCC’s finding that the planet is indeed warming, there are still skeptics. Many of these critics cite temperature fluctuations dating back millions of years. Marinov agrees that there were times in the past when temperatures and CO2 were higher than today, but argues this is only part of the story. “When dinosaurs were on the planet, it was very warm,” she says. “There’s no way a human civilization would have developed then. The gradual cooling of the Earth over the past 50 million years, together with a recent warming in the past 10,000 years, have uniquely converged in a climate perfect for the development of modern civilization. Besides the better-known implications of a warmer climate such as sea levels rising, glaciers melting, and ocean acidification, there are large nonlinearities in the system that we don’t have control over. If we continue on our current path of carbon emissions and climate warming, we are setting ourselves up for disaster.”
