When forecasting climate change, scientists usually opt to determine what the climate will look like at a specific point in time, for example in 2050, or in 2100. In a new study, however, researchers linked local changes directly to the prevalence of global warming. “It does not matter whether two degrees gets reached in 2040, according to a more pessimistic projection, or in 2070, or in 2090 according to a more optimistic projection. What counts is what happens to Estonia’s climate once that level is reached,” explained the study’s lead author, Erko Jakobson, associate professor of atmospheric remote sensing at the university.
The principal finding is that Estonia’s annual mean temperature has been going up by about one-and-a-half degrees for every one degree rise in mean temperatures globally. At the same time, periods of very cold weather will become increasingly rare, while hot days, tropical nights and heatwaves are to get more frequent. In other words, during the warmer part of the year, climate change can already be observed with your own eyes, not to mention felt firsthand in Estonia alone.
Observable climate change
In order to create a picture of the future, the researchers ran 31 global climate models. Jakobson noted the public’s expectations regarding the accuracy of climate forecasts are unfortunately often far in advance of what current science is capable of delivering. “Some local governments want us to tell them, right down to the village level, how the climate will change in this or that location. We cannot do that – even if it were mathematically viable to do it at the county level, it would not be meaningful, and we would essentially be telling lies,” Jakobson explained.
The analysis revealed also that Estonia’s winters are warming several times faster than its summers. For every additional degree of global warming, Estonia’s average winter temperature rises by 1.9 degrees Celsius, while its summer temperature rises by 1.3 degrees Celsius. The number of freezing days falls by 13 percent for every degree of warming. While milder winters help save on heating costs, they may bring issues of their own, not least to winter sports enthusiasts – though currently active skiers are not likely to see completely snowless winters as a rule, in their lifetimes.
“We forecast a decline in the number of cold days, and we do not actually know whether snow will fall during those cold days. In any case, even under the most pessimistic forecasts, Estonia should continue to see snow until the end of the century. But the fact that we used to have long periods without thaws will be but a fond memory for skiers,” Jakobson noted. Even more convoluted challenges await farmers, as the milder conditions actually threaten winter crops: The insulating layer of snow will be replaced by more damaging freeze-thaw action.
A warming climate more generally and globally brings intensified precipitation too. For every additional degree of global warming, precipitation in Estonia rises by an average of approximately 31 millimeters, or 4.6 percent.
This precipitation falls mainly in winter and the fall, but the models remained unclear about summer projections. Estonia’s location plays a key role here. “We looked at the bigger picture, meaning the entire Baltic Sea region and points south. It clearly emerged that the dividing line runs more or less through our area: In summer, it becomes drier to the south and wetter to the north,” the scientist said.
Erko Jakobson Source: Personal collection.
In any case, Estonia’s summer hydrological picture is set to become more contrasting. Short, heavy downpours wash soil and nutrients off fields while failing to alleviate drought stress in plants.
“Instead of periods of steady rain, half of the precipitation will often fall within a few hours. That water does not have time to soak into the ground but immediately runs into ditches and rivers, doing more harm than good to fields. The drought problem therefore actually increases,” Jakobson warned. The stronger evaporation characteristic of a warmer climate may cause problems for farmers especially in spring and summer.
The dynamics of air masses, however, continue to pose a considerable challenge for climatologists. Estonia’s weather is shaped simultaneously by strong Atlantic cyclones and high-pressure systems to the east. Precise changes in atmospheric circulation and wind behavior are therefore difficult to capture with physical models.
“There is a great deal of uncertainty regarding changes in circulation, and I do not see a good prospect of the forecasts becoming much more certain. Our latitude means that our weather is not made here but comes from elsewhere. Everything depends on whether weather coming from the north or the south gains the upper hand,” the researcher added.
Because of the uncertainty, it cannot currently be said that Estonia will experience stronger winds and storms in the future. In summer and autumn, average wind speeds may even decrease slightly. “One very widespread belief is that it will become windier in the future. In some ways, that is logical: there is more heat and energy. In our work, we saw that some models show wind speeds increasing, while others show them actually decreasing. We therefore cannot confirm that winds in Estonia will indeed become stronger and storminess will increase,” Jakobson said.
Bigger questions
Jakobson stressed the projections in the models are based on continuous trends, but the climate system contains a number of tipping points. “If the Antarctic ice sheet or Siberian permafrost melts significantly, or the Gulf Stream changes substantially, enormous quantities of greenhouse gases could be released. Current climate models have not accounted for such abrupt changes, so there may still be surprises,” the associate professor warned.
Jakobson noted that scientific facts and the future scenarios presented by climate models unfortunately tend to become mixed up with day-to-day politics in public debate. Instead of assessing physical reality, people argue over the economic consequences of the green transition.
Scientists’ task, however, is to measure the causes and pace of warming, while finding solutions and allocating resources remain the responsibility of society and politicians. “When large sums of money are involved in politics, fraudsters sometimes get involved and things go wrong. But the fact that something goes wrong in politics unfortunately does not mean that climate change does not exist,” the scientist said.
The study was first published in the journal Boreal Environment Research.
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