Guest essay by Eric Worrall
A new study claims that while the US West will feel the impact of Climate Change by 2028, Southern Great [Plains] region won’t notice Climate Change until 2074.
When will the US feel the heat of global warming?
For the Great Plains, natural variability will dominate until late this century.
JOHN TIMMER – 3/21/2018, 6:55 AM
By increasing the energy stored in our atmosphere, climate change is expected to generate more severe storms and heat waves. Severe storms and heat waves, however, also happen naturally. As a result, it’s tough to figure out whether any given event is a product of climate change.
A corollary to that is that detecting a signal of climate change using weather events is a serious challenge. Are three nor’easters in quick succession, as the East Coast is now experiencing, a sign of a changing climate? Or is it simply a matter of natural variability?
A team of researchers has now looked at heat waves in the US, trying to determine when a warming-driven signal will stand out above the natural variability. And the answer is that it depends. In the West, the answer is “soon,” with climate-driven heat waves becoming the majority in the 2020s. But for the Great Plains, the researchers show that a specific weather pattern will push back the appearance of a warming signal until the 2070s.
To quantify this difference, the authors developed a simple measure: the year in which half of the heat waves wouldn’t have qualified as heat waves if it weren’t for the influence of climate change. For the US West, that point was crossed in 2028. The West was followed by the Great Lakes, which crossed the threshold a decade later in 2037. But the Great Plains were on a completely different schedule. In the Northern Plains, the 50-percent threshold wasn’t crossed until 2056, while the Southern Plains didn’t have a clear signal of climate change until 2074.
So why is internal variability so significant in the Great Plains? The researchers suggest two potential causes of these regional differences. One is a difference in the flow of air across the continental US, something that may be changing with our warming climate. If the prevailing winds become more erratic, then it’s possible that they would bring cooler air across the Plains more often. The alternative is soil moisture. This takes up heat from the air and ground as it evaporates, which would counteract some of the heating caused by greenhouse gases.
The abstract of the study;
Early emergence of anthropogenically forced heat waves in the western United States and Great Lakes
Climate projections for the twenty-first century suggest an increase in the occurrence of heat waves. However, the time at which externally forced signals of anthropogenic climate change (ACC) emerge against background natural variability (time of emergence (ToE)) has been challenging to quantify, which makes future heat-wave projections uncertain. Here we combine observations and model simulations under present and future forcing to assess how internal variability and ACC modulate US heat waves. We show that ACC dominates heat-wave occurrence over the western United States and Great Lakes regions, with ToE that occurred as early as the 2020s and 2030s, respectively. In contrast, internal variability governs heat waves in the northern and southern Great Plains, where ToE occurs in the 2050s and 2070s; this later ToE is believed to be a result of a projected increase in circulation variability, namely the Great Plain low-level jet. Thus, greater mitigation and adaptation efforts are needed in the Great Lakes and western United States regions.
Read more (paywalled): https://www.nature.com/articles/s41558-018-0116-y
So much for the climate emergency – if the study is correct, if you live in the Southern Great Plains and you are lucky enough to live until 2074, you might notice the weather has warmed slightly.