Links Between Climate Change and Drought Not as Cut and Dried
The natural conclusion is that as global warming gets worse so too will the droughts. We’ve even had evidence of it, right? Droughts in Australia, the US, and horribly dry conditions throughout Europe.
However, new research from Princeton University and the Australian National University in Canberra suggest things may not be as cut and dried as we first thought.
The problem is that the reports of increasing numbers of droughts were caused by weaknesses in the mathematical model that has been used to simulate drought – the Palmer Drought Severity Index – rather than there being any real drying trend.
“The overall view has been that as temperature increases drought is going to increase,” said Justin Sheffield, a research scholar in Princeton’s Department of Civil and Environmental Engineering. “But it is not that simple.”
Their research was recently published in the journal Nature, where they reported that errors resulting from the Palmer model had led to overestimates of the severity of drought worldwide.
Wood said that better models are available for climate scientists to use, but the Palmer Index is frequently used because of its simplicity, however that same simplicity is the reason errors have crept in.
First developed back in the 60s, the Palmer Index relies heavily on temperature data to allow it to estimate the extent of drought. One of the reasons this is the case is because at the time temperature data was relatively easy to acquire. However it has also made the Palmer Index extremely sensitive to warming.
This heavy reliance on temperature, Sheffield said, is “where things start to go wrong.”
“Many other things are changing — wind speed, solar and infrared radiation, humidity of the air,” Sheffield said. The Palmer Index, he said, “is too simple a model to take these changes into account.”
In fact, issues with the Palmer Index are representative of much of climate science and prediction at the moment. With more research comes the greater understanding that we don’t understand nearly as much as we had hoped or thought. The more we study, the more we find the climate is an almost-overwhelmingly complex mechanism that doesn’t necessarily obey the sciences we understand.
To deal with the inaccuracies in the Palmer Index Wood and his group at Princeton have designed a more sophisticated model that includes inputs for data such as solar radiation, humidity, and wind – inputs well beyond the scope of the original Palmer Index which help give it a much wider and more accurate picture of conditions on the ground.
“You can go a long way by using a more physically realistic approach, a more appropriate approach, to make these estimates,” Wood said.
“It certainly does not mean that things are not going to be bad in the future,” Wood added. “It does not negate the idea that we are having an impact on the atmosphere and that this will have an impact on drought.”
This research also does not diminish the terrible droughts already in place and recent. It was only in November of last year that the US drought was found to be worsening and affecting wheat crops, as well as the energy markets.
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