The Environmental and Conservation Issues Room
Statistical evaluations are used to determine the relationship between weather extremes and climate change. The media finds a causal relationship always, scientists sometimes. Several examples are considered.
Weather Is Not Climate. Or is it?
First the technical stuff.
Examples....Friederike Otto, an Oxford University climate researcher associated with the World Weather Attribution (WWA) collaboration, told MIT Technology Review in 2020. "So the question of the role of climate change will never be a yes or no question. It will always be, 'Did climate change make it more likely or less likely, or did climate change not play a role?'"
For the last decade or so, climate researchers like Otto have been working on statistical techniques aimed at estimating the extent to which a warmer world is making weather events more extreme and/or increasing the frequency of such events. One technique is to run climate models using the current levels of atmospheric greenhouse gases to see if they reproduce the relevant observed weather trends for a region. If the models accurately track the actual record of weather events, the researchers next run them assuming pre-industrial greenhouse gas concentrations. The differences in, say, the maximum temperature during a heat wave, the amount of rainfall dumped by a hurricane, or the timing and extent of wildfires provide an estimate of how much man-made warming may contribute to specific extreme events.
And so on with mixed results.Consider the massive heat wave in June 2021.... Under pre-industrial conditions, WWA researchers found, the chance of a heat wave like that was essentially zero. "Western North American extreme heat [was] virtually impossible without human-caused climate change," they concluded.
Other notable 2021 extreme weather events in the U.S. included Hurricane Ida, which slashed the coast of Louisiana in August; a massive December outbreak of tornadoes in Kentucky; and the Colorado wildfire that destroyed 1,000 houses just outside Boulder in late December. Are all those events also strong examples of weather as climate?
...Studies "provide limited evidence of anthropogenic effects on [tropical cyclone] intensifications so far," the IPCC report notes, "but high confidence for increases in [tropical cyclone] heavy precipitation." In other words, the evidence that global warming is causing hurricanes to spin up faster is currently weak, but the evidence that it boosts rainfall during hurricanes is stronger....
Climate models are too coarse and observational data too sparse to draw firm conclusions about how climate change may be affecting tornadoes. The IPCC report notes that the annual average number of tornadoes in the U.S. has remained constant since the 1970s, although their location appears to be shifting from the Great Plains toward the mid-South, which includes Kentucky.
Fire weather involves a combination of high temperatures, drought, and low humidity. From 1979 to 2013, the global burnable area affected by long fire-weather seasons doubled, and the average length of the fire-weather season increased by 19 percent, according to research cited by the IPCC. Despite climate change "at the global scale," however, "the total burned area has been decreasing between 1998 and 2015 due to human activities" such as agricultural expansion and intensification.
Politics.
In a May 2021 Climatic Change article, Otto and her collaborators observe that extreme event attribution studies have three primary uses: answering questions from the public, providing information on how to adapt to future weather extremes, and, last but not least, "increasing the 'immediacy' of climate change, thereby increasing support for mitigation."...
...[But] Economic growth and technological innovation already have enabled people to thrive as they adapt to extreme weather events. As a result, noted Copenhagen Consensus Center President Bjorn Lomborg in a 2020 Technological Forecasting and Social Change article, the chance that a person might die from climate-related risks such as floods, droughts, storms, wildfires, and extreme temperatures has fallen by more than 99 percent since 1920.
Attribution research is increasingly able to tell us how climate change is affecting the likelihood of extreme weather events. But it cannot tell us how best to handle them.
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Originally Posted by Chris
