Between 1998 and 2013, the global average surface temperature, one of several measurements used to gauge how much the Earth has warmed, grew more slowly than we expected. That has had scientists asking a lot of questions.
The period has become known as the global warming hiatus. This is an inaccurate name for what a recent international study has deemed a “global surface warming slowdown.”
“The hiatus period gives scientists an opportunity to understand uncertainties in how climate systems are measured, as well as to fill in the gap in what scientists know,” says study lead author Xiao-Hai Yan of the University of Delaware, Newark.
It turns out that the reason for the global warming hiatus in that period is that the oceans were making up for it. The earth’s energy system is very complex, and the oceans are a big part of it. For the record, the earth’s energy system is how energy from the sun interacts with the planet and is sequestered in various oceanic, atmospheric, and terrestrial methods.
For much, if not most, of the Earth’s history, that energy system was very carefully balanced. In the last century and a half, it’s become unstable due to the increased creation of greenhouse gases like carbon dioxide and methane. While these gases always naturally exist, they have increased because of human activity, which is the basis of the current global climate change crisis.
That period between 1998 and 2013 saw slower change because the oceans, which are perhaps the most efficient part of the Earth energy system, sequester an increasing amount of carbon dioxide. However, the oceans can only sequester so much CO2, and there is too much in the atmosphere for the ocean to absorb it all. They will continue to sequester CO2, but as that rate increases, the water is going to become warmer and more acidic. This is already having a widespread and negative impact on the global ecosystem.
The scientists behind the study are calling for increased focus on measuring water temperatures as part of understanding the changing climate.