Earth's climate: running hot and cold
'We are picking on the climate with our carbon emissions'
The future of the Earth's climate is an extremely complicated picture that is difficult to predict when all factors are considered.
Recent scientific reports have shown some effects that will add to global warming, while others show cooling effects.
It underlines the complexity of the Earth's climate and unintended effects from human activity.
A report in the journal Nature found that ocean circulation in the North Atlantic is weakening, which could result in a cooling effect on the climate of Europe.
The Atlantic meridional overturning circulation (AMOC), often referred to as the conveyor belt, is a system that brings warm water from the tropics northward in ocean currents such as the Gulf Stream that run along the surface.
Colder water from the Arctic returns south along the bottom of the ocean completing the conveyor cycle. But over the past half century, the strength of the AMOC has reduced by 15 per cent, which is affecting the flow of warm water to the north.
A complete shutdown of the conveyor was over-dramatized in the movie The Day After Tomorrow which took it to the extreme as only Hollywood can, but the basic concept was sound.
Strangely, the cooling effect that can result from shutting down the conveyor is caused by warming in the atmosphere.
Glaciers in Greenland are melting faster than ever before, which combined with disappearing ice in the Arctic Ocean, is adding freshwater to the surface of the ocean.
Freshwater is less dense than saltwater, so it doesn't sink to the bottom, which blocks the conveyor system. That means cold water can remain in the north longer, less warm water comes up from the south, and Europe freezes. Maybe.
At the same time, another report out of Dalhousie University has shown that ocean heat waves are on the rise, leading to further warming.
The oceans have a form of liquid weather similar to what we see in the atmosphere, where warm and cold areas jostle for position around the planet in a never-ending cycle that includes heat waves and cooling periods. So while some areas of the ocean may get cooler, others are warming up.
Finally, a study out of Norway, which we feature on Quirks & Quarks this week, shows that the burning of fossil fuels — largely responsible for trapping heat in the atmosphere — also produces fine particles called aerosols that drift in the atmosphere and act as a sunscreen to block sunlight and provide a cooling effect.
But as cities around the world work to clean up air pollution with the removal of these aerosols, the sunscreen effect will cease, causing more warming.
All these conflicting warm and cold effects on the climate might make it look like science contradicts itself. And these apparent contradictions are often used by climate change deniers.
But on the contrary, it shows how complex the climate system of the Earth really is, and how poorly we understand the connections between the atmosphere, the oceans, the land, and the life around the globe.
In the words of conservationist John Muir, "When we try to pick out anything by itself, we find it hitched to everything else in the universe."
We are picking on the climate with our carbon emissions, and it is affecting everything else in the system in more ways than one.
That is why it is called climate change rather than global warming.
In the end, reducing carbon emissions solves a whole range of other problems along the way.