Why Hasn’t Spring Gotten Warmer?

April 23, 2013
By Georgine Yorgey

Agriculture is a seasonal endeavor.  And so the weather during each season can profoundly impact farmers and the crops they produce.  Now, researchers at University of Idaho and Oregon State University are providing some new insights on how the seasonal climate has changed over the last century in the PNW, and how it might change over the next 50 years.

John Abatzoglou and his collaborators at Oregon State have analyzed the climate data for the Pacific Northwest by season over the last century.  For the most part, their results are likely not a surprise.  Annual temperatures warmed, as did summer, fall, and winter, and the rate of warming increased over time.  But they also found one major exception, in spring. Temperatures in spring have cooled slightly over the past three decades, most notably since the early 1990s. Cooler springs during the last few decades affect cropping decisions, timing of field operations like planting or spraying, and pest cycles.

Why is this? There are lots of influences on the climate, including volcanoes, solar output (the total radiation coming from the sun, which can vary based on sunspots and solar flares), known large-scale climate cycles (such as El Niño and the lesser known Pacific North American pattern), and human caused greenhouse forcing (the factor most prominently associated with global climate change).

Their analysis (see a factsheet here and presentation summarizing the results here) suggests that the cooling is largely the result of natural large-scale climate cycles. In the absence of these cycles, spring warming would have likely occurred, at about the same rate as predicted by climate change models that consider greenhouse gas emissions.  You can see these cycles in spring temperature clearly in the graphic below, showing mean spring temperatures in Lewiston, Idaho. The mean springtime temperature for the entire time period was 52°, and you can see departures from that mean for each year (red bars for years when the mean temperature exceeded 52°, blue bars for years when it was below 52°).  The black line denotes the 11 year running mean and makes the cycles evident, with periods during which there are cooler-than-average spring temperatures followed by periods when there are warmer-than-average temperatures. (Similar data for other locations in the Northwest is available here).

spring warm graphic

Better understanding these climate cycles, and the combined impact of multiple drivers on seasonal climate, is of critical importance to agricultural producers, particularly in light of a changing climate. The natural factors that have resulted in cooler springs are not likely to continue indefinitely. Instead, it is likely that when these processes reverse, and large-scale natural factors and human caused greenhouse forcing are acting in the same direction, we will see significant seasonal warming.

Filed under Climate Change

4 comments on “Why Hasn’t Spring Gotten Warmer?”

  1. Jim Devany said on April 24, 2013:

    How does the present temperature situation stack up here in the Columbia Basin?

  2. Delbert said on April 24, 2013:

    DO not try to feed me this BS about human caused global warming. I am sick of hearing it from you who would have no job aside from this made up, invented “phenomenon”. Get a clue and spend your time and money on something that helps us be productive instead of how we are causing “global warming”!! Do not waste my tax dollars or industry dollars on this. We do not control or influence the climate! He who created this earth made it how he made it and we are not capable of destroying it! Give me some useful information next time that I can pass along to my farmers!!

  3. Georgine Yorgey said on April 24, 2013:

    Dear Jim,

    While there is a lot of variability/noise in the data, the same general pattern holds for spring in the Basin. Here’s a time series showing the mean spring temperatures averaged over the Middle Columbia Basin: http://www.wrcc.dri.edu/wwdt/time//regionsBargraph/?region=17070106&variable=1&start_year=1895&end_year=2012&month=5&span=3&run_avg=11

    Note that you see something quite different if you look at the calendar year. Here you can see a time series showing the mean annual temperature averaged over the Middle Columbia Basin. Though you still see the natural climate cycles, you can also see an overall warming trend: http://www.wrcc.dri.edu/wwdt/time//regionsBargraph/?region=17070106&variable=1&start_year=1895&end_year=2012&month=12&span=12&run_avg=11

    You can also look up spring temperature series for individual locations in the Basin at the link I provided above (http://www.wrcc.dri.edu/research/jtwrcc/idaho-mon/index.html), or explore the weather data for larger areas at http://www.wrcc.dri.edu/wwdt/time/.

  4. Boyd Walton said on April 24, 2013:

    I live in Omak wa—I,ve farmed for 47 years–I am not a expert on the weather,but I live it every day—my observations–winters warmer than 25 years ago –summers not as hot but dryer—spring cooler–I use to quit feeding beef cows around the first of april–know it is the last of april—I am sure this weather change is caused by the number of people working for the government in washington DC

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