Global warming will intensify drought … Possibly. Maybe. Perhaps.

drought

Last IPCC report assigned only low confidence on an increase in frequency of droughts. In the skeptic blogosphere this became quickly known and distributed. The mainstream media didn’t seem to pick this up, it was obviously not in the press release. A couple days ago I came accross an article that seemed to defy this statement. It was the article Global warming will intensify drought, says new study from John Abraham.

I was rather curious why droughts would be increasing. Did some new evidence popped up since AR5? Was there something that other studies missed? What proof did this particular study found that was contrary the IPCC statements in AR5? Did investigators had new insights? Looking at the name of the author of the article I feared this could be a one-sided article. My fear became reality. Already in the second sentence a clear attribution of human emissions on heat waves and changing rain patterns was stated. This is how the article starts (my emphasis):

When scientists think about climate change, we often focus on long term trends and multi-year averages of various climate measures such as temperature, ocean heat, sea level, ocean acidity, and ice loss. But, what matters most in our day-to-day lives is extreme weather. If human-caused climate change leads to more extreme weather, it would make taking action more prudent.

It is clear that human emissions have led to increased frequencies of heat waves and have changed the patterns of rainfall around the world. The general view is that areas which are currently wet will become wetter; areas that are currently dry will become drier. Additionally, rainfall will occur in heavy doses. So, when you look at the Earth in total, the canceling effects of wetter and drier hides the reality of regional changes that really matter in our lives and our economies.

Something that caught my eye was the changed focus from global climate to local weather. We heard a long time from GLOBAL warming. Now the author has an explanation if there are no global changes. Just say that local weather counts more. Speaking of moving goalposts. If local weather extremes are attributed to global warming, there is no limit on what one can prove.

The study he hinted at in the title was from Trenberth et al.: Global warming and changes in drought. It was behind a pay wall, so not freely available to look at.

It seems to discuss the different ways that droughts are measured. In the paper, Trenberth documented five different teams coming with five different conclusions.

One reason for this was the different base period (1950-2008 and 1950-1979) taken by the investigators. I can imagine this. This is logical. Different base periods can give different results, I seen this before.
A second reason was the limited availability of the data.

Basically, the conclusion was that climate change impacts our live, so it is important to have more data.

Hey…wait…with all the different results of those five different teams and the uncertainties from a lack of data, how could Abraham ever come to the conclusion that, ahem, “Global Warming will intensify drought”?!?! That doesn’t fit.

Confused about this article I searched for more information about the paper. I found another article: Still Uncertain: Climate Change’s Role in Drought from Bobby Magill (ClimateCentral, also not exactly a skeptic site). This article with quotes from the author gives a whole new perceptive on the story then what we seen in the Abraham article:

It’s common for direct connections to be drawn between climate change and the effects of the devastating droughts that have been afflicting the U.S. and other parts of the world over the last decade. A new analysis led by scientists from the National Center for Atmospheric Research says there are still many uncertainties about how climate change is affecting drought globally, though.

The analysis, authored primarily by NCAR senior scientist Kevin Trenberth, concludes that more global precipitation data need to be made available and natural variability needs to be better accounted for to fully determine how climate change is affecting drought worldwide.

“We are really addressing the question of, how is drought changing with global warming and expected to change in the future?” Trenberth said Friday. “To address that question, how is drought changing with global warming, you have to address the question, is drought changing?”

[…]

Trenberth’s paper concludes that changes to the global water cycle in response to global warming will not be uniform. The analysis noted that the differences in precipitation between typically wet and dry regions and seasons will likely increase, but climate change is unlikely to directly cause droughts in the near future.

That is something completely different. The article seem to be about acknowledging the uncertainty of global warming on droughts. And yes, Trenberth assumes the difference drought/precipitation will likely increase. But this is his initial assumption, not yet confirmed by the data (because not enough data is available yet to do so).

To be clear, this is not his conclusion, as Abraham seems to suggest, but the assumption he starts from!

Big difference.

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