Climate Change Will Cause Increased Flooding In Coastal Cities
A new paper by prominent climate scientist James Hansen and colleagues says even a moderate increase in global temperatures could lead to much greater sea level rise than the most recent Intergovernmental Panel on Climate Change (IPCC) report predicts. Since the IPCC report (last published in 2013) is based on the work of thousands of climate researchers, many people are skeptical of the new paper. Again, this isn’t because they doubt climate change is real or that sea-level rise is a big problem. Instead, the critics’ concerns are about the details of the model Hansen and his coauthors use.
Based on current trends, Hansen and colleagues modeled how quickly ocean levels are rising. They considered the rate of ice sheet melting in Greenland and Antarctica, along with increases in water temperature. Comparing those present data to models of climate and ocean levels in ancient times, they conclude sea levels could rise several meters in the next century. That catastrophic increase would happen even if global temperatures are held to the conservative limit of 2° Celsius increase, proposed as a reasonable goal by many agencies.
The broad outlines of the paper are within the norm for climate research, but the details are at odds with other studies. The obvious disagreement is the amount of sea level rise, which in this paper is a much higher rate of increase than other models show. Kevin Trenberth of the National Center for Atmospheric Research (NCAR) writes that the new paper mishandles important short-term climate fluctuations such as the El Niño phenomenon, which can make individual years much warmer than the average. In other words, record-breaking temperatures this year are specifically from El Niño, but the general increase in global temperatures is part of the trend due to climate change.
James Hansen is well known for his role in bringing scientists’ worries over climate change to a much wider audience, when he testified before Congress in 1988. He has stated that this new paper could be his most important work, an understandable sentiment. If the results of this paper are true, then rapid sea-level rise will disrupt the lives of huge numbers of people around the world, and governments need to take action immediately.
But that of course is where things can get sticky. Historically, climate scientists have been more conservative than not in making public statements to avoid alarmism and giving fuel to powerful denialist voices. They may not have science on their side, but those who claim either that climate change isn’t real or say it’s not a big problem have a lot of money and media platforms. The deniers happily pounce on any tiny misstep, real or perceived, by climate researchers and those of us who report on their findings.
Another paper, published yesterday in Nature, had less fanfare than the Hansen paper, but shows the severe danger of flooding in coastal regions, particularly in the United States. This risk isn’t directly from sea-level rise, but from the intensification of storm surges and increased precipitation that are secondary effects of climate change. Flooding risk in any particular place depends on a number of factors: the flatness of land right by the water, how steep the continental shelf is off the coast, the number and severity of storms, etc. That’s why much of the state of Florida is at greater risk than coastal cities in California.
As the Nature paper shows, heavier rainfall combines with storm surges, the rush of water toward the shore during major storms, to amplify flooding. That combination is deadly: thanks to climate change, storms are more frequent, and with sea-level rise, flooding is going to get much worse. To put it another way: we don’t need the ocean to rise several meters to create severe floods. The next decade of hurricanes and tropical storms could bring the effects of climate change right into coastal cities.
About 40 percent of the population of the United States lives in coastal counties, and many of the world’s major cities are similarly close to the ocean. Even if the critics are right and the alarmist predictions from Hansen and colleagues aren’t correct, we’re not out of trouble.
Fonte. Forbes
