Climate Change and Climate Cycles
We have heard a lot about global warming in the past few years. Then, in mid-November 2019, we saw cold temperature records shattered in much of the Central and Southern United States. Concurrently, parts of Asia and much of Eastern Europe were experiencing abnormally high temperatures. How can we put this all in perspective with respect to global climate change? Here is a little background.
Late in the year 406 A.D. over a frozen Rhine River, many accounts state that Germanic tribes crossed into Gaul. This was the initial invasion into the Roman Empire, that would eventually lead to the Empire’s fall. If the Germanic tribes had waited 100 years, it would have been more difficult as the Rhine then rarely froze solid. Climate had changed and temperatures were rising.
By the year 800 A.D. what is known as the Medieval Warm Period had started. Mild temperatures prevailed until about 1300A.D. In Europe, crops thrived and populations increased. The Vikings colonized Iceland and Greenland. Then things again began to change. Beginning around 1400 and lasting until the middle of the 19th century, a cool period set in. New crops were devised to survive the cold and the Dutch began reclaiming land from the sea to provide more land for raising crops. This period was known as the Little Ice Age. It reached its peak from the years 1645 until 1715. Glaciers advanced and destroyed alpine villages in France and Switzerland. The extreme cold and advancing glaciers were associated with what is known as the Maunder Minimum in sunspot activity.
Solar temperature is directly related to sunspot activity. With a warmer sun, we see more sunspots. Most scientists believe both the Medieval Warm Period and the Little Ice Age resulted from changes in the sun’s radiation, associated with the number of sunspots. Other contributions may have come from the level of volcanic activity. When a strong volcanic eruption occurs, sulfur dioxide expelled into the stratosphere may form droplets of sulfuric acid. These droplets help block incoming solar radiation. During the Little Ice Age, for example, the sun was colder than normal and volcanic activity was higher.
We must consider that the climate is always changing. To reflect this, the National Climatic Data Center recalculates precipitation and temperature averages every ten years using the previous 30 years’ data. For example, in 2011, climatic averages were calculated using data from 1981 through 2010. In 2021, they will be recalculated again using data from 1991 through 2020.
Many scientists believe the current warming is due to an increase in greenhouse gases such as carbon dioxide and methane. However, the sun reached a peak in warmth during the 20th century that was comparable to the warm sun of the Medieval Warm Period. For the past four solar cycles, each lasting about 11 years, the sun has been cooling, and today the sun is as cool as it was over 200 years ago. Some scientists think this solar cooling will offset any anthropogenic (human-caused) effect we are currently seeing and may put at least a temporary halt to global warming.
So what does the future hold? We know the effects of a cooler sun are delayed, but we should be seeing them soon. Will it be enough to halt, or even reverse, global warming? The answer remains to be seen, but any effect will last only as long as the sun remains cool.
Sunspots picture (https://www.nasa.gov/mission_pages/sdo/images/index.html)