Low solar activity usually leads to cooler weather, but other historical trends and factors like El Niño, hurricanes, and greenhouse gases are keeping this year at relatively normal temperatures.
Low Solar Activity and Colder Weather
Solar activity has been very quiet this past year. As you may know, we at The Old Farmer’s Almanac use solar activity as the driver of our long-range weather forecasts. We believe that changes in the Sun’s output, although relatively small, are sufficiently amplified in Earth’s upper atmosphere to strongly influence Earth’s weather patterns.
One of the most significant relationships we have found is that periods of low activity are associated with colder temperatures, averaged across Earth. Our viewpoint is a controversial one, as most scientists believe that the magnitude of changes in solar activity are insufficient to have a significant effect on Earth’s weather, and they view as coincidence that past periods of exceptionally low solar activity have historically coincided with cold periods.
As you can observe in the accompanying graph below (from the NASA Marshall Spaceflight Center), recent solar activity has been at its lowest levels in at least a century. The lowest recorded activity occurred over 300 years ago in the so-called Maunder Minimum (named for English astronomer Edward Walter Maunder, 1851–1928). This was also an exceptionally cold period in many parts of the globe.
Photo Credit: NASA. Recent solar activity is at very low levels.
The second accompanying graph below (also from the NASA Marshall Spaceflight Center) shows the data for the officially numbered sunspot cycles, from Cycle 1 in the mid-1700s to our current Cycle 24. As you can see, the current cycle is comparable to the very low levels of solar activity that occurred in the early 1800s (the “Dalton Minimum,” named for English meteorologist John Dalton, 1766–1844, which coincided with the “Little Ice Age”) and early 1900s. These three periods have brought the lowest solar activity levels since the Maunder Minimum.
Photo Credit: NASA Marshall Spaceflight Center. Three have been 24 recorded sunspot cycles.
Historically, all of the periods in the known sunspot record that have had low activity have also had relatively cool temperatures, averaged across the globe. We believe that with low solar activity continuing for at least the next 10 to 30 years, global temperatures will be cooler than they would otherwise be. Find out more about the solar activity forecast for 2016.
Other Factors: Volcanoes, Greenhouse Gases, El Niño, and Hurricanes
So why, you might ask, was this past winter so mild in most of the continent, with solar activity so low? The answer is that solar activity is not the only factor in Earth’s weather.
For example, one factor that all atmospheric scientists believe can make Earth colder for as much as a few years is a volcanic eruption that spews ash into the middle and upper portions of the atmosphere. Volcanic ash actually played a major role in causing the famous Year Without a Summer. While this has not been a major factor in recent years, it could be in the future.
The most significant factor, in addition to solar activity, that has been affecting our weather in recent years has been the increase in “greenhouse gases,” most notably carbon dioxide and methane, which most (but not all) atmospheric scientists believe has been making Earth progressively warmer. As the effects of this climate change have continued to grow, we have been incorporating it into our forecasts, as a factor that will offset much of the cooling from our current period of low solar activity.
In fact, despite our low solar activity, May 2016 marked the 13th consecutive time that this month was the warmest that it had ever been, averaged across the globe, since we have been keeping records. Amazingly, the last month in which the global average temperature was below its average for the 20th century was back in February 1985, more than 30 years ago (this is all according to NOAA, the U.S. National Oceanic and Atmospheric Administration, the parent agency of the U.S. National Weather Service).
Although the fact that Earth, on average, has been warming for decades does not mean that every place will be warmer than normal each season. The strong El Niño of this past winter, which anchored the pattern in place that made this past winter so much warmer than normal in much of the United States and Canada, has been replaced with a strengthening La Niña, which will help to make next winter much colder than this past one. Learn more about the roles of El Niño and La Niña in determining our weather.
Another difference between the two patterns relates to hurricane and tropical storm activity: During an El Niño event, Atlantic/Gulf action is minimized, but it is generally above average in La Niña conditions. This will be a factor in the current hurricane season, especially as the La Niña strengthens. So, do not be surprised if hurricane activity continues into November.
However, the reverse is the case for Pacific hurricane and tropical storm activity, with a less active season during La Niña conditions. So, we expect minimal tropical moisture in California this summer and early fall, with dry weather this winter adding to the severity of that state’s drought. For more detailed information on this year’s tropical storms, check our hurricane forecast for 2016.
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