Effects of global heating on the streams and rivers of Europe
Streamflow increases in the north and decreases in the south
Recently, scientists looked at how stream flow has changed in Europe, due to global heating. They examined the changes from 1950 to 2013. The year of 1950 is well after humans had started pumping CO2 into the atmosphere, but the data on stream flow from back then is pretty reliable; so it can be a good starting point. And, well, you have to start at some point in time. Back then, CO2 levels were at 310 ppm, certainly higher than the historic level that hovered around 280 ppm, but far from the 415.58 ppm that we face in today’s headlines.
Computer modeling has predicted reduced flows in southern and eastern Europe and increased flows in central and northern Europe. And at least one recent observation has indicated these trends.
Overall, what the scientists found confirms the other science, that stream flows have decreased in southern Europe, in the countries that lie around the Mediterranean, and increased in northern Europe, in places like Scandinavia. Most of Great Britain and Ireland have seen greater stream flows, with notable decreases around the southern portion of England, around London and Plymouth.
Data for the project was gathered from 3913 gauged stations across the continent. After a quality control assessment, 428 stations were eliminated, because they had gaps in data or there were other reasons to believe that the numbers they had were unreliable. Results showed that 95 percent of the streams had a trend, with 70 percent of those having more stream flow and 30 percent having less. The scientists published their findings in the journal Hydrology and Earth Systems Sciences in October.
When they looked at the data, season-by-season, the researchers found that almost all European rivers and streams had increased flows in winter. In areas where flows have reduced, things start to decrease in April, reaching their lowest flows in August. This means that for the 30 percent of drier waterways the overall stream flow is not only lessened, but that the overall stream flow is also more extreme.
You might ask if measuring the change in precipitation might give us a better idea of what’s going on, but measuring the stream flow is actually a good idea. We learn of the change in water available for homes, irrigating farms, and other uses. Change in stream flow can also give us an overarching understanding of the overall effects of climate change. Stream flow will of course change if there is a change in the amount of rain or snow. It will also change if the climate warms or chills.
Even without climate change, humans have affected the rivers and streams of Europe for centuries. (And, for that matter, you can add the streams and rivers of the rest of the world, too.) People have dammed rivers and drawn from them for drinking and irrigation. As with the rest of the developed world, European rivers are prone to what is called flashiness. In natural conditions, when it rains, the soils of the forests, shrublands, and grasslands soak up some water before it starts to flow downhill and meet up with a creek or river. Because of this sponge-like quality, during and after a storm, the flow of a river will rise gradually and decrease gradually.
People build roads, buildings, parking lots, and lots of other hard surfaces that don’t soak up water. Rainwater flows off directly, causing rivers to rise quickly. Without the storage capacity of soils, once a storm is over, the stream flows drop dramatically as well.
What do the headlines say?
OK, that’s the data. What are the headlines telling us? Wildfires in the Mediterranean consistent with a warmer, drier climate are happening in times and places that they had not before. In Spain this year, there have been fewer than normal fires, but the number of large fires has increased by 36 percent, with an increase of 4,000 more hectares burned. Drought is also affecting groundwater and ecosystems. In Italy, wildfires accompanied an extreme heat wave in August. (Sicily reported a temperature of 119 Fahrenheit.) And northern Europe is getting bouts of too much water. Germany made headlines this year with record breaking and catastrophic flooding; there are similar occurrences in Britain.
With such consequences of global heating—the floods in Germany alone are estimated to cost more than $33 billion—it would seem that the politicians attending the COP26 conference in Glasgow would be champing at the bit to reduce emissions. But, as Greta Thunberg points out, COP26 amounted to a whole bunch of Blah, Blah, Blah.
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