Humanity relies heavily on the ocean and its inhabitants, who man in turn is putting at risk by changing the climate. That’s according to Ove Hoegh-Guldberg, director of the Global Change Institute at the University of Queensland, who points out that global warming and ocean acidification pose “serious threats to life in the ocean”. “Both of those are having profound effects on the biology of the ocean and on the ocean services which are important to human well-being,” he told Simple Climate.
In fact, some of these effects have happened so fast that Hoegh-Guldberg has seen them unfold during the course of his career. For example, corals are normally highly coloured, but have been turning white and dying as they lose the microorganisms that inhabit them and provide them with energy and food. “When I started my PhD in the early 1980s, mass coral bleaching events were just beginning to occur across tropical regions,” he explained. “We now know that those are being driven by warmer than normal sea temperatures and that they are slowly removing coral dominated communities from tropical reefs, at the rate of 1-2% per year. Given that this is the most biologically diverse ecosystem on the planet, I think that these rates are striking.”
Together with his Queensland colleague John Bruno, Hoegh-Guldberg recently reviewed how life in the oceans is responding to climate change for top journal Science. There they highlight that the average temperature of the upper layers of the ocean has increased by 0.6°C over the past 100 years. While this has been bad news for coral, some creatures have moved to new areas of the ocean. Sometimes, they can live more successfully in their new locations than creatures that would normally live there. However Hoegh-Guldberg warns that such “invasive species” can also be seen as a problem, potentially invading fisheries and affecting industries such as agriculture. “This does not negate the fact that we are losing some of the most spectacular ecosystems on the planet,” he added. “Very few species are thriving as result of these changes.”
Ocean acidification and global warming can both be blamed on a common cause – increasing CO2 levels in the atmosphere. The oceans absorb around 30% of the CO2 that humans produce. Dissolving CO2 in pure water produces an acidic mixture. The oceans are slightly alkaline, so the acidification arising from dissolving more CO2 actually forces them closer to neutral. The Queensland researchers write that the measured changes arising from this “represent a major departure from the geochemical conditions that have prevailed in the global ocean for hundreds of thousands if not millions of years”.
Meanwhile, Hoegh-Guldberg has a suitably simple explanation for the impact of increasing atmospheric CO2 levels on temperatures. “When I’m explaining global warming, I like to use the analogy that the Earth has a sweater or pullover, which is the atmosphere,” he said. “As the sun shines, some of that energy is trapped by the sweater/pullover/atmosphere. Emitting CO2 is like adding more wool to the jumper, and as you do that, more and more energy is trapped and the temperature begins to heat up.” Worryingly, Hoegh-Guldberg also notes that recent research shows the oceans taking up less CO2 than they used to, meaning that more of what we emit will add straight on to this “sweater”.
Despite the straightforwardness of his explanation, Hoegh-Guldberg has little time for those who suggest that it might be flawed. “As a trained scientist, I have not seen a single shred of evidence that successfully challenges both the theory and evidence of climate change,” he asserted. “Those that deny the existence of climate change refuse to look at the peer-reviewed scientific literature. This is the same literature that’s given us modern medicine and spaceflight. One wonders why you can believe in one set of scientific outcomes, and then ignore another.”
To limit climate change, Hoegh-Guldberg says, action begins at home and work. Everyday concerns like how we buy our food, power our electronics, and transport ourselves have a big part to play. The scientist has put solar panels on the roof of his house, paid to offset the CO2 emissions from his travel through actions like planting trees, and rides a bike to work. “It will also be important that we vote for those politicians that get this issue,” Hoegh-Guldberg says. “To vote for anyone else at this point is to throw the future of this planet and our children away.”