In the Two Minute Drill, we explain complex issues in politics in 500 words or less (roughly the amount of words it takes the average adult two minutes to read on a monitor). Politics just isn’t always that complicated. Without the fluff and partisan bias, even the most complex of our political differences can be explained succinctly. This week: extreme weather, event attribution, and climate change. This is The Two Minute Drill for March 18, 2016.
Extreme weather and climate events – such as heat waves, droughts, heavy rainfall, hurricanes, etc. – have always posed risks to human society. A matter of growing interest to the scientific community and public at-large, however, is the degree to which humans are changing these risks through anthropogenic climate change. Can we attribute an extreme weather event to climate change?
The Explanation (500 or Bust)
Extreme weather is one way that people experience climate change, and some of the reasons for changes in extreme weather events are well understood. For example, warming is expected to increase the likelihood of extremely hot days and nights, lead to more evaporation that may exacerbate droughts, and increase atmospheric moisture that can increase the frequency of heavy rainfall and snowfall events. However, in general, whether or not anthropogenic climate change has influenced an individual weather or climate event is extremely difficult to determine. It involves consideration of a host of variables that combine to produce the specific conditions of an extreme weather event – events that are rare by definition, meaning that there typically are only a few examples of past events at any given location.
In many cases, this means that a definitive answer to the commonly asked question of whether climate change “caused” a particular event to occur cannot usually be provided in a deterministic sense. However, climate science has advanced to such a degree that unqualified blanket statements – such as, “we cannot attribute any single event to climate change” – are no longer true. “In many cases,” according to a recent report from the National Academy of Sciences, “it is now often possible to make and defend quantitative statements about the extent which human-induced climate change . . . has influenced either the magnitude or the probability of occurrence of specific types of events or event classes.”
In other words, science is beginning to understand and address the following questions regarding attribution: “Are events of this severity becoming more or less likely because of climate change?” and “To what extent was the storm intensified or weakened, or its precipitation increased or decreased, because of climate change?”
According to the NAS, confidence in attribution analyses of anthropogenic influence is greatest for specific extreme events that are related to an aspect of temperature (e.g., extreme cold events and extreme heat events) where there is little doubt that human activities have caused an observed change. There is a significant, though not as high, degree of confidence for events that are related indirectly to temperature (e.g., droughts, extreme rainfall, extreme snow and ice storms). But there is little confidence in the attribution of severe convective storms, wildfires, and extratropical cyclones – events where there are significant limitations in the historical data.
Given the relative newness of the event attribution field, the NAS researchers cautioned against drawing general conclusions about the impact of climate change on extreme events as a whole. However, while the ability to understand these extreme events is still evolving rapidly, it is becoming clear that attribution studies can be a tool for informing choices, assessing and managing risk, and guiding adaptation strategies in a warmer climate.
Word Count: 456
[Last Modified: March 19, 2016 for length/typos.]
CHART IMITATES LIFE
Below are a few of the charts and relevant explanations from the National Academy of Sciences report (which you can read for free as a .pdf from the NAS website). The charts below are indicative of the seriousness of climate change, and demonstrate the urgency of the problems we face.
In case you missed it, check out The Weekly Column. This past week took a look at “border security” and immigration. Read the Column for March 15, 2016 – “Border Security” Is a Red Herring in the Immigration Debate.
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