Planet Earth is getting hotter. One of the more confusing aspects of this global trend is the persistent, undeniable discomfort of winter. Even more confusing is when that chilly weather continues into April, May, or godforbidpleasenot June.
This might clear the confusion (but probably not the frustration): Those colder temperatures in the first half of the year might be due to warmer weather in the Arctic. Authors of a new study, published Monday in Nature Geoscience, found this trend looking at over 100 years of climate data from the Arctic and North America. This warm Arctic/cold North America connection has been particularly noticeable since 1990. And that doesn’t just mean you’ll be wearing a puffy jacket to Memorial Day cookouts from now on. Spring is an important time for agriculture, and the authors noted that US crop productivity declined by as much as 4 percent following warm Arctic years. Plus, those crops, along every other plant affected by the connected weather cycles, absorb less CO2—Arctic warming begets the potential for even more warming.
The Arctic is warming faster than anywhere else on the planet. This causes problems, because that big gob of cold air messes with large scale atmospheric circulations in the latitudes the US occupies. “The Arctic warming has a remote impact via atmospheric teleconnection,” says Jong-Seong Kug, an environmental scientist at Pohang University of Science and Technology in South Korea, and co-author of the new paper. Atmospheric waves, induced by polar forcing, convey signals to the middle latitudes.” What kind of signals? Well, the upper atmospheric waves could alter the position of key high or low pressure zones on either side of the North American continent. This would have huge consequences for how large scale weather systems travel, altering not just temperature, but precipitation, cloud cover, and a myriad of other ecosystem changes.
To make sense of how the Arctic was affecting North America, this study pulled data from a set of climate models called CMIP5. “These compile everything going on with Earth’s climate: human emissions of fossil fuels, interactions between the atmosphere and ocean, radiative forcing, clouds, and so on,” says Anna Michalak, a climate scientist at the Carnegie Institution for Science in Stanford, and co-author of the new paper. CMIP5 is necessary for this kind of research because it averages out the flaws of each individual climate model—Earth is too complicated for any one of them to replicate perfectly. “Let’s say you are trying to get a headcount of all the people who attended a rally, and you ask one person,” says Michalak. “That person’s count might be a bit off. But if you talk to 10 or 15 different people, you can get a good sense of the range of people who were there.” CMIP5’s operators ran the multi-model against historical data in order to vet the thing’s accuracy. Other researchers analyze smaller chunks of this massive database in order to make sense of how intercontinental climate systems interact.
The new research compared observational temperature data from the Bering Sea with temperature and plant growth data from the US from 1990 to 2010. They saw a pronounced trend of generally cooler winters and springtimes in the northern US and Canada, and dry weather around Texas and neighboring states. In terms of plant growth, these weather patterns stunted about 14 percent of the aggregate US ecosystem’s ability to uptake carbon dioxide.
And then there are the farms. Using historical state-level crop yield data from the National Agricultural Statistics Service of the United States Department of Agriculture, the researchers found that warmer Arctic years were associated with a 1 to 4 percent overall decline in agricultural yield across the US. But those are just the averages. Some states, like Texas, experienced as much as 20 percent decline. This kind of research could be used by farmers to plan accordingly—they could watch for warm Arctic winters, and plant later in the spring, for instance. But that’s no guarantee: The authors point out that their work merely identifies a trend. Weather cycles are notoriously complex, and don’t work in simple cause/effect relationships.
Still, you probably want to know what happens when you project the model forward in time. Wanna guess? Yep, things get worse. Warmer Arctic seems to result in even colder North American, and much more damage to plants. Of course, these scientists are modelers, not oracles, and it’s hard for them to model the effects exactly. “The vegetation growth does not linearly respond to the climate factors,” says Kug. “For example, when the temperature decrease about 10%, the vegetation damage does not increase by 10%. It may cause much more damages than 10%. We call this is nonlinear response.” Different species will respond to cooler springs, or hotter summers, in different ways. Some might migrate, some might die off, some might kick their production into overdrive. But that’s not much to warm the soul.
Full Story: US Farms Could Suffer as the Arctic Heats Up