“It didn’t use to be this hot when I was younger.” I have heard that phrase for as long as I can remember. I can only assume that the ice ages must not have been as long ago as I had originally been taught.
In all seriousness, has the average temperature changed in these summers since global warming? Has spring gotten shorter? And what is an Indian summer?
To answer those in reverse order, an Indian summer is a period of unseasonably warm, dry weather that sometimes occurs in autumn in the Northern Hemisphere. These are weather conditions that are sunny and clear with above normal temperatures, occurring late-September to mid-November, usually after a killing frost.
Average summer temperatures have been rising in every region of the United States since 1970. Though they have all gotten hotter, there were some remarkable differences in how much. Southern California and Nevada have summers that are over 5°F hotter than they used to be. In the Upper Midwest, on the other hand, the average is only 0.1°F per decade. Averaged together, the country’s summers have been warming by 0.4°F each decade, for a gain of nearly 2°F since the cooler days of 1970. So if you look at the long-term scale, summer really is hotter than it used to be.
However, where you are makes a difference in how that increase is experienced, and there are classifications for those climates. The Köppen Climate Classification System is the most widely used system for classifying the world’s climates. Its categories are based on the annual and monthly averages of temperature and precipitation. The Köppen system recognizes five major climatic types; each type is designated by a capital letter.
A – Tropical Moist Climates: all months have average temperatures above 18° Celsius
B – Dry Climates: with deficient precipitation during most of the year
C – Moist Mid-latitude Climates with Mild Winters
D – Moist Mid-Latitude Climates with Cold Winters
E – Polar Climates: with extremely cold winters and summers
There are many factors that determine the climate of a particular place. These factors include:
1) Latitude and its influence on solar radiation received
2) Air mass influences
3) Location of global high and low pressure zones
4) Heat exchange from ocean currents
5) Distribution of mountain barriers
6) Pattern of prevailing winds
7) Distribution of land and sea
No matter how the categories are defined, climate classifications help people know what types of weather to expect. Besides vacation planning, knowing a region’s climate classification is useful when choosing building materials that will last through expected conditions, or when considering what crops are more likely to thrive in a region.
It is interesting to point out that climate classifications are not etched in stone. As a region’s temperature and precipitation patterns change, climate classifications based on those parameters will also change. Comparing past, present, and future ranges of plants and animals can also show changing classifications. Scientists are currently observing changes in ecological relationships that are linked to our changing climate. For instance, the trend of earlier budburst in spring for certain plants must be matched by the maturity of insects that depend on nectar from those flowers, or the insects will lose their food supply. As temperature and precipitation patterns change, so too will ecosystems, and the climate classifications that are based on them.
So when your elders remind you that they didn’t have summers like this and they had to walk uphill to and from school in the blinding snow, you can go ahead and chuckle, but they aren’t all wrong.
Melody K. Smith, Blog Wrangler