Global warming is heating up the Arctic, which in turn is causing cooler, drier weather for the rest of North America.
That’s the conclusion of a new study which finds that over the past three decades, years in which the Arctic experienced abnormally warm weather translated into “more frequent and more intense” cold spells for the rest of Canada and the United States, which in turn resulted in significant declines for agricultural crops.
The study conducted by an international team of researchers from South Korea, China and the US compared sea-surface temperature readings in the Bearing Sea with annual records on crop production and temperature for the years between 1990 and 2010. They found that during times when the Arctic waters were unusually warm, weather patterns to the south were disrupted in turn, producing cooler winters and springs for Canada and the northern US as well as drier weather for the south central United States.
Although separated by thousands of kilometres, the weather systems of the north and south are linked by atmospheric circulation which during winter months brings colder air down from the north. But with the heating up of the planet through the greenhouse effect, more sea ice is melting in the Arctic during late summer and fall, which sends more cold air to the lower parts of the continent.
That translates into more severe winters for Canada and the northern US along with lower precipitation for south central US states like Texas, both of which have had their impact on crop production across North America for staples like corn, wheat and soybeans. The researcher shows that crop yields in affected areas of the continent fell by between one and four per cent, with some states in the US experiencing declines of up to 20 per cent.
Overall, the researchers say that plant life in temperate zones of North America experienced a decline in capacity to absorb CO2 of around 14 per cent.
“We find that positive springtime temperature anomalies in the Arctic have led to negative anomalies in gross primary productivity over most of North America during the last three decades, which amount to a net productivity decline of 0.31 petagrams (PgC) per year across the continent,” say the study’s authors, whose research is published in the journal Nature Geoscience.
The study’s climate modelling suggests that the same scenario affecting crop productivity should only become more pronounced as warm spells in the Arctic become more the norm and plants sensitive to changes in precipitation and temperature are impacted. “There will be more frequent and stronger cold events [in North America], induced by the Arctic warming,” said climate scientist Jong-Seong Kug of Pohang University in South Korea and study co-author, to the Washington Post.
Around the globe, the vulnerability of food and crop production is increasingly being exposed by severe weather patterns deemed to be brought about by climate change. Notably, research suggests that more pronounced droughts and heat waves will likely have a bigger impact on industrialized farming in regions like Canada, the United States and Europe. The argument goes that whereas productivity in the developing world is impacted more by issues such as insect pests and soil fertility, the high-yield, single-crop farming practices in the industrialized world are more strongly affected by water issues such as drought and, to a lesser extent, flooding.