Count On Sea Levels To Keep Rising For A Long Time

by Bob Talbot, Professor of Atmospheric Chemistry Director, Institute for Climate and Atmospheric Science, University of Houston

The world’s oceans have been warming for decades. Increasing water temperatures – driven by higher emissions from a variety of greenhouse gases – have caused the oceans to thermally expand. Glaciers and other previously frozen areas are melting, aggravating and accelerating the rise of the ocean surface.

Fossil fuels are a key contributor to the warming, but they are not the only one.

Scientists now track ice across the Arctic and Antarctica, and what they are finding isn’t encouraging. Last year was the warmest year ever recorded for the global oceans, a phenomenon linked to a number of potential problems, including damage to important habitats such as coral reefs and risks for certain animal populations.

In addition, the Arctic Ocean is expected to be ice-free during the summer within the next 20 years.

Rising sea levels are among the most visible signs of climate change, as well as one that will have a dramatic impact on humans.

And it’s happening faster along the Gulf Coast – home not only to the nation’s fourth-largest city, Houston, but also home to much of the nation’s critical energy infrastructure – than anywhere else in the United States, between 5 millimeters and 10 millimeters per year.

Eventually, cities such as Galveston will be underwater, and the rising waters also will impact the Port of Houston’s operations in coming decades. This is the largest U.S. port in terms of tonnage handled each year, and the amount is increasing due to enhanced Panama Canal ship traffic.

The same thing is happening along the Florida Keys, where areas are already flooded today. Hurricane Irma facilitated the erosion of beaches and other low-lying areas.  Today residents are driving to the local grocery store with many inches of seawater on the roadways in many locations, and although efforts to raise the roads are underway, it won’t be cheap.

All of this is just the tip of the iceberg.  The worst is yet to come. And the economic impact on the United States could be dramatic.

The causes are complex. That means the solutions – and the timeline for any possible recovery – are complex, too.

Fossil fuels are a major contributor to the problem. Carbon dioxide and other greenhouse gases are being added to Earth’s atmosphere at alarming rates as the world continues to burn crude oil, coal and natural gas. Indeed, the annual increase in carbon dioxide is at its highest rate ever. That has pushed the Earth out of radiative equilibrium – ideally, the heat coming to Earth from the sun is equal to the amount of heat that returns to space. Because carbon dioxide and other greenhouse gases trap some of the heat that is trying to escape our atmosphere, the radiative equilibrium is out of balance.

But the causes go beyond fossil fuels. Global agriculture is also a growing problematic source of methane and nitrous oxide, two powerful greenhouse gases. The ever-expanding population of Earth will not stop, and these people need to be fed.

And not all greenhouse gases are equal. Methane, for example, is a more potent greenhouse gas than carbon dioxide, but it also degrades in the atmosphere within a decade or so. Cutting methane emissions would, therefore, show results relatively quickly.

Carbon dioxide and nitrous oxide are different, and their warming effects will remain intact for future generations. This is because they are essentially chemically unreactive in the troposphere, or the lowest part of Earth’s atmosphere, where we live. Moreover, carbon dioxide is most soluble in cold oceanic waters, which are diminishing. Warmer ocean waters means the oceans can absorb less carbon dioxide.

Estimates of this are highly uncertain, but the full warming effect of an emission may not be felt for several decades, if not centuries.

What does this all mean?

Sea levels will likely continue to rise for many centuries into the future.  Don’t get wet.


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