Apparently, methane is not a harmless gas since one of its side effects is that it causes sea levels to rise for centuries.
Now the reports every week say that glaciers are melting in Greenland and Antarctica. Coastal areas will see sea levels rise due to this in the future. In fact, it is happening right before our eyes.
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Yet there is a hidden factor that also causes sea levels to rise. This has been termed thermal expansion. When greenhouse gases go into the atmosphere, they cause air temperature to rise. A bit of this heat is absorbed in the oceans and causes water to expand.
Anyone who has made a cup of tea knows that hot water expands in volume. It is one of the simplest laws of physics. Thermal expansion is something the scientists have to take care to include in their models for future sea level rise.
Yet the real issue is how long this phenomenon lasts. The problem is that even if greenhouse gase emissions are cut radically by human beings, the effects would last for centuries.
The process seems to be an irreversible one. Such greenhouse gases as methane that don’t last long in the atmosphere will have an impact for centuries in the future.
The oceans will bear the brunt of the burden. The message we get from this study is that the ocean has a long term memory. Experiments were carried out to see which gas had more of an impact on the ocean.
Such gases as methane, carbon dioxide, nitrous oxide and halocarbons were dealt with. In the computerized model simulations, these gases were hypothetically continuously monitored till the year 2050 in the future.
As compared to carbon dioxide, the other gases have short atmospheric lives. Methane stays for only 10 years while carbon dioxide stays for 200 years.
Yet the oceans show the impact for centuries afterwards. 100 years afterwards, 75% of the thermal expansion caused by methane still persists. 40% remains after 500 years.
This has a lot to do with the way the ocean behaves. Ocean currents and the flow of warm water is what comes into the mix. Thus the importance of curbing greenhouse gases has become even more of a necessity.
In the late 80s, the Montreal Protocol was signed to see to it that this crucial step was taken. Yet on the whole, more needs to be done even now.
The findings of this study appear in the journal Proceedings of the National Academy of Sciences.