2015-08-16 08:57:59
While some continue to debate what makes us human, we can well say that one of the characteristics of our species is to reveal reality while denying it when it does not suit us. For example, Humanity has been denying death since it was aware of it. Today, he insists on denying realities that, however, due to his invincible stubbornness, will end up being imposed, as it cannot be otherwise.
One of the facts that has been tried to be denied by some who do not care about this fact is climate change. In reality, it is not so much climate change that they deny as that its causes are due to human activity, in particular the emission of greenhouse gases, especially carbon dioxide (CO2). About two years ago, the observatory located on the Mauna Loa volcano in Hawaii determined that atmospheric CO2 levels had exceeded 400 parts per million (ppm). Today they exceed 403. I remember that when I was little, I think it was in the third or fourth year of high school, they taught me that the CO2 levels in those years were about 325 ppm. Thus, in the course of my still not very long life – which on a geological scale is and will be only a mere moment – the levels of CO2 in the atmosphere have risen by more than 20%. It is evident that this CO2 arises from the use of fossil fuels as a source of energy. We know how many barrels of oil and tons of coal we have burned and the amount of CO2 that their combustion has caused, and that value and the atmospheric increase are coherent. It has also been demonstrated that this gas does not allow heat in the form of infrared radiation to leave the planet easily, which ends up increasing its average temperature. It is true, there have been other times on Earth of important climate changes; The one we are experiencing is not the only one that the planet has suffered, but it seems clear that, on this occasion, the causes are not geological, but biological: the acts of our insatiable animal species.
However, although having determined the primary causes of global warming is important, it is also important to try to predict its consequences. Thus, scientists who are dedicated to the study of climate know that it, in the different regions of the planet, is very dependent on the circulation of marine currents. Does global warming affect these currents, which could in turn lead to other, less obvious climate effects?
Marine currents originate precisely from temperature differences between different regions of the Earth. Seawater warms in the tropics, causing it to stay at the surface, but water cools at more northern latitudes, causing it to sink to the bottom. It is the water that sinks due to the cold in the north that causes the water that has warmed in the south to direct there, thus generating gigantic currents, like that of the Gulf. This current transports heat from the tropics to our latitudes and beyond, and is what makes countries like Ireland, Scotland, Norway, Sweden or Denmark reasonably habitable in winter.
Fresh water circuit breaker
Atmospheric warming due to the increase in CO2 is having an important effect on the ice that melts from Greenland and is dumped into the North Atlantic. The water from this melt is fresh, so it floats above salt water due to its lower density. This fresh water accumulated on the surface of the ocean acts as a barrier to the northward progress of the Gulf Stream, which, being salt water and encountering less dense fresh water on the surface, sinks prematurely. because it has cooled, but because it is denser. This premature sinking could prevent the heat carried by this current from reaching higher latitudes, which would cause a cooling of these areas, which would not be able to receive the heat from the current, and a warming of the tropical areas, which would not be able to evacuate their excess. of heat. In other words, the average temperature of the planet would be higher, but some areas would be much hotter and others colder than normal. The distribution of heat would be less homogeneous on a planetary scale.
A recent study published in the journal Nature Climate Change indicates that this is what is happening. While the water temperature in the tropical areas of the Atlantic has warmed to breaking records, the opposite has happened in the North Atlantic, which has also broken records, but for the coldest temperatures. The study’s authors estimate the intensity of the Gulf Stream over the past few centuries by measuring changes in coral reefs, tree rings, and other parameters that can indicate the distribution of heat in the ocean. What they find is that, according to these parameters, the Gulf Stream has declined significantly since 1970. The authors estimate that, if this trend continues, there is at least a 10% probability that the Gulf Stream stop completely by the end of the century.
Of course, if it were to happen, such a situation would cause significant climate changes in our latitudes, perhaps irreversible changes that will lead to serious social, economic and even political imbalances. Climate change is not just a matter of temperature.
Referencia: Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation. Stefan Rahmstorf et al. Nature Climate Change 5, 475–480 (2015)
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