Many gardeners and farmers will recognize the tendency toward global warming as a good thing. Crops may be easier to grow and get established especially when the new warming becomes something on which we can depend. I’m not sure we are there yet. Even while such warming trends have been hard to deny, gardeners and farmers everywhere are still uncertain about when the last killing frosts will occur and so continue to make plans as usual. We are still trying to discriminate annual from long term patterns.
Still, crop yields have often been better when new warmth makes it a good year. Also, steady and sufficient or even increased rainfall, have improved the health, time to maturity and yields of crops. In the recent past those same crops may have been stunted by excessive rains or even dry conditions in the face of either warming or cooling trends to which crops often poorly adjust. In some cases as conditions improve, one might even plant later when the danger of frost is well past, and still have exceptional crop yields. As time to maturity improves, one may be well out of the field and even have time to lay down a green manure crop after a steady but not back-breaking harvest schedule.
In North America near the Canadian-U.S. border, both to the north and south of it, the weather is moderating, and provided adjustments in rainfall levels follow the warming, new or improved agricultural regions may gradually take shape. However, adequate rainfall may or may not follow warming trends. Farmers and gardeners may be cautious in the uptake in adjusting crops and strategies. Yet, while we are likely to see some changes in what crops are planted and when, it will likely be some time, if ever, before new tropical favorites take over the landscape. We will not see orange groves in Central Montana! Rather, we are likely to see slow changes, but with considerable experimentation by gardeners and farmers as weather patterns change. We know already that there are more persistent El Nino patterns that create pronounced westerly and often much milder winter weather patterns across the lower 48 and warmer, wetter weather through northern U.S. and southern Canada during the winter months. Such patterns also suppress southerly bends in the Arctic jet stream. That tends to keep all of North America in a generally warmer winter pattern.
However, the persistence of warmer surface water over the Arctic Ocean and the increasing open and ice free in regions north of eastern Siberia have increased early fall high pressure patterns in north-central and eastern Russia. This can lead to steering of early cold, winter winds across the Arctic and into western Russia and Europe. Such patterns can bring especially harsh snows and blizzards across the region. We don’t really know enough yet to say whether these patterns will last year after year or if they will shift from year to year or even if they are related in any way to adjusting El Nino — La Nina patterns.
We do know that what is happening in the Arctic will change weather all through the Northern Hemisphere, making it warmer and more moist. Increasing open ice regions of the Arctic during the summer months will increasing absorption of solar radiation and increased warming of surface waters. A cool fall and spring will continue as will occasionally harsh winters–but perhaps not as harsh as they used to be. The Arctic is being transformed from a cold, barren ice desert into a more moderate but still generally cold region. Biomass will increase and move increasingly to the north. Areas previously unsuitable for gardening or agriculture may gradually give in to short growing seasons with conditions improving as one moves to the south. Associated possibilities of increased rain and snowfall may also be a benefit to agriculture in the longer term as well. Persistent changes in weather patterns that occur in longer term are not likely to be completely clear for years or even decades.