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Sunday January 26, 2020 – Attribution Science - With the
wildfires in Australia still burning deniers are already starting to scoff at
the idea that some how these wildfires were the result of global warming.
In a way they are correct, the wildfires were not started by global warming.
There are multiple causes for the start of the wildfires. Some were started by lightning strikes while others were possibly started by arsonists, and still others were no doubt started by accident. The cause of the fires are not the only thing we need to consider though. We also have to consider the severity of the fires and how that severity was impacted by a warming planet.
The science behind this is called attribution and what it does is to apportion the blame for the severity of the event. Australia has bush fires every year but his year was extraordinary burning an area greater than the state of West Virginia. The question to ask is not what started the fires but how much worse were they than if global warming had not happened. It all boils down to a matter of percentages.
Scientists are busy working on how much worse the Australian wildfires were because of climate change but there have been plenty of other catastrophic events in recent years where attribution science has been applied to determine how much worse the even was made due to the effects of CO2 being pumped into the atmosphere.
Attribution studies look at the past occurrence of similar events and comes up with a probability that the event will occur. For example if a category 5 hurricane hits an area on average once every 100 years the probability that it will hit in any given year is 1%. Now, if the history is split into two periods, one before global warming became significant and one after and the frequency of a given event is larger or smaller there is a good chance that the difference was attributable to human caused warming.
Once the frequency of an event is shown to have increased or decreased the scientists can then use a computer model to see what the difference would have been if the amount of greenhouse gases in the atmosphere has stayed constant or increased to current levels. The difference can then be expressed as a percentage which would say that the probability is that the event was more or less severe is a given percent.
Many people are looking for a solid Yes or No to the question "was this event caused by global warming" but there is no true yes or no answer. What attribution science tells us is that the probability that the event was made worse is X%.
For example, hurricane Harvey hit Texas in 2017 dropping an unprecedented amount of rain along the gulf coast. This event was subject to attribution studies that showed the severity of the rain increased by at least 19% over what it would have been had greenhouse gas levels stayed as they were in the 1950s.
Climate scientists have been telling us that the increased temperature caused by the emissions of greenhouse gases will likely make events like hurricanes, wildfires, and droughts more severe. Attribution science when applied to such events is proving this to be true. We need to take broad action to reduce fossil fuel usage or the world that our great grandchildren grow up in is going to be distinctly less pleasant than the world of today.
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