![]() And that’s not just a snapshot, it’s a trend. If you’ve been following the National Center for Environmental Information’s monthly reports (and you should!), you may have noticed that this year’s extensive warmth in the western United States is driven by extremes in minimum (overnight low) temperatures, even more so than maximum (afternoon high) temperatures. Colder times of day are warming more than warmer times of day Since the turn of the 20 th century, the nation’s average winter (December through February) temperature has increased by almost twice the rate of the summer (June through August) temperature, at 2.0☏ per century versus 1.1☏ per century, respectively. Graph by NOAA, based on NCEI Climate at a Glance data. (Inset) Trends since the start of the twnetieth century for the four seasons. Seasonal temperatures from 1895-2014 compared to the twentieth-century averages (gray lines). ![]() This shows up clearly in the US temperature record, particularly during the last quarter-century, when the excursions from the long-term average are much larger during the winter season than the summer. In most of the mid-latitudes, where most Americans live, and where we have something resembling four seasons each year, the cold season is warming the most rapidly of all. Colder seasons are warming faster than warmer seasons The rate of warming with elevation in general is complex – probably too complex to qualify as a rule of thumb, but there is evidence that high-elevation places are warming more, on average, than lower elevation places. On mountains themselves, there is a noticeable effect of increased warming at mountain stations near the average snow/no-snow line, which is leaning more toward no-snow– and thus, additional warming–in recent years. The migration of seasonal snow lines isn’t just a north-south latitude thing it’s also an up-down altitude thing. But the map of temperatures from the most recent completed decade (2000-09) also hints at (remember: we’re talking rule of thumb here) the effect of additional warming across traditionally seasonally snow-covered areas in Siberia. The graph above clearly shows the Arctic region’s steeper temperature climb. Graph by NOAA, adapted from Figure 1.1 in the 2014 Arctic Report Card. ( bottom) Yearly October-September temperatures compared to the 1981-2010 average. NASA Earth Observatory map, based on data from NASA GISS. ( top) Arctic amplification of climate change evident in map of 2000-2009 temperatures compared to the 1951-80 average. As the white stuff goes away, it exposes darker surfaces and land cover underneath this introduces an additional warming effect across the region. This “Arctic amplification” is driven by a handful of factors the largest of these is the retreat of seasonal snow and ice. ![]() The Arctic is warming at more than twice the rate of the rest of the world. ![]() This rule of thumb is really dominated by the fact that the arctic is the fastest-warming large region on the planet. Colder places are warming faster than warmer places With that definition and some horrible puns out of the way, let’s thumb through some data. Local exceptions to the rule may be in the minority, but they don’t completely stick out like a sore thumb because in certain local situations, the facts can be … wait for it … opposable. So, it's nothing to thumb your nose at, because it’s true more often than not. This one is pretty simple to put your thumb on: on average, cooler places and cooler times are warming more quickly than warmer places and times.īut first, let’s clarify–and emphasize–what we mean by a “rule of thumb.” Just like in its common usage, a rule of thumb here refers to something generally true often enough to be useful and informative, but not universally reliable–kind of a “two-out-of-three” or “three-out-of-four” kind of situation. This week, Beyond the Data looks at one of the more well-grounded “rules of thumb” for understanding climate change. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |