Public Release: 12-Dec-2018
Record-wet and record-dry months increased in regions worldwide
Climate change drives rainfall extremes
Potsdam Institute for Climate Impact Research (PIK)
More and more rainfall extremes are observed in regions around the globe – triggering both wet and dry records, a new study shows. Yet there are big differences between regions: The central and Eastern US, northern Europe and northern Asia have experienced heavy rainfall events that have led to severe floods in recent past. In contrast, most African regions have seen an increased frequency of months with a lack of rain. The study is the first to systematically analyze and quantify changes in record-breaking monthly rainfall events from all over the globe, based on data from roughly 50,000 weather stations worldwide. Climate change from fossil fuel greenhouse gases has long been expected to disturb rainfall patterns.
„We took a close look at observed monthly rainfall data – if it’s not just a few days but several weeks that are record wet, this can accumulate over time and lead to large river floods, or to droughts if it is record dry,” says lead author Jascha Lehman from the Potsdam Institute for Climate Impact Research (PIK). The impacts on people’s livelihoods in the affected regions can be huge, ranging from flooded houses to endangered food security due to large-scale agricultural losses.
Downpour in parts of US, Europe, Russia – drought in parts of Africa
The US has so far seen an increase of record wet months by more than 25 percent in the Eastern and central parts over the period 1980-2013. Argentina and bordering countries have experienced an increase of 32 percent. In central and northern Europe the increase is between 19 and 37 percent. In the Asian part of Russia the increase is around 20 percent, while South East Asia shows an increase of about 10 percent.
The scientists ran strict tests for the statistical significance of observed changes. Therefore, they so far see significant changes in dry extremes just in Africa south of the Sahara and in the Sahel zone where dry records have increased by up to 50 percent. „This implies that approximately one out of three record-dry months in this regions would not have occurred without long-term climate change,” says co-author Dim Coumou from the Institute for Environmental Studies (IVM) at Vrije Universiteit Amsterdam. „A central conclusion from our study is that, generally, land regions in the tropics and sub-tropics have seen more dry records, and the northern mid- to high-latitudes more wet records – this largely fits the patterns that scientists expect from human-caused climate change.”
UN climate summit decides about future rainfall extremes
The scientists compared observed wet and dry rainfall extremes to the number of extremes that would be expected in a climate without long-term changes. „We checked for new records – monthly rainfall values that have never been observed before in a given region since the beginning of systematic measurements more than a hundred years ago.” Of course one expects to see some rainfall records simply due to natural variability. „Normally, record weather events occur by chance and we know how many would happen in a climate without warming,” explains Jascha Lehmann. „It’s like throwing a dice: on average, one out of six times you get a six. But by injecting huge amounts of greenhouse gases into the atmosphere, humankind has loaded the dice. In many regions, we throw sixes much more often with severe impacts for society and the environment.”
„It is worrying that we see significant increases of such extremes already at just one degree global warming,” adds Lehmann. „Right now, governments from countries all over the world meet at the UN climate summit – if they do not agree on solutions to limit warming to well below 2 degrees, we’re headed for 3-4 degrees within this century. Physics tells us that this would boost rainfall extremes even further.”
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Article: Lehmann, J., Mempel, F., & Coumou, D. (2018): Increased occurrence of record-wet and record-dry months reflect changes in mean rainfall. Geophysical Research Letters, 45.
Weblink to the article, once it is published: https://doi.org/10.1029/2018GL079439
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This is record keeping and torturing data with statistics, but I see no science done here and the conclusions are mere speculation and arm waving.
In fact, they don’t even say in the abstract the time period observed but instead say “Sparse rainfall data, however, have made it difficult to answer the question of whether robust changes can already be seen in the short observational time period.”
Ron, it seems they took individual rainfall data for particular months (The more unreliable the further back you go.) and calculated the long-term averages. They defined some greater or lesser numbers as “extreme” and applied them to fit their meme.
In other words: “You can’t see our data, methods or computer programs.”
I am WOKE to their methods.
“The scientists compared observed wet and dry rainfall extremes to the number of extremes that would be expected in a climate without long-term changes.”
And what method did they use to determine what would be expected without long-term changes? The phony IPCC “with and without CO2” model runs?
“It is worrying that we see significant increases of such extremes already at just one degree global warming.”
If global temperature causes global weather, then how is it that global weather does not repeat when temperatures rise or fall to the levels they have been at previously? If you believe BEST or HADCRUT 4, then the temperature spike that occurred around 1876 was nearly matched in the early 1940s, and then again around 1980, after which temperatures continued to go up by an additional 0.5C or more. And yet, the horrific global drought and bizarre meteorological conditions that obtained in the 1870s (e.g. Minnesota farmers ploughing fields in December of 1878) were never repeated, either in the 1940’s, the 1980s, or thereafter.
The same goes with the freakish weather of the 1930s, the global temperature of which was supposedly matched and exceeded in the latter half of the 20th century, yet without any similar weather phenomena emerging.
Does this not suggest that either:
a) the temperature series on which we compare past to present are wildly incorrect; or
b) meteorological conditions, such as rain and drought, do not emerge from “global temperature” at all but are simply local phenomena and unrelated to global temperature?
Additionally, if CO2 is well mixed in the atmosphere globally, and if small increases in global heat cause local weather phenomena to change, then is it to be supposed that those changes, having taken place, become immutable? If, for example, a 0.2C increase in global temp has somehow caused more rain clouds to form over the area where I live, then is it not equally possible that an additional 0.2C increase might cause those clouds to move somewhere else? Perhaps even move somewhere, God forbid, that could use a bit more rain?
On what basis is it even possible to say that increasing CO2 / temp will cause a particular area to become wetter or drier, if that prediction is not made in specific reference to a particular concentration of CO2 or a specified global average temperature? Has it been determined that weather in each location can change as a result of CO2 increasing from 350 to 400ppm, but that from that point onward all changes are either immutable or only allowed to become “even more so” but not “even less so”? Seems to make very little sense.
Of course you will see increasing records over time in some areas. Just like you will see decreasing records in other areas.
What you are measuring is variability, not climate. The same result would be found regardless of CO2.
we know how many would happen in a climate without warming
=≠=======
Actually you don’t, because you don’t have data from an earth that wasn’t warming.
What you have is an earth that has been warming since 1850 and rainfall data for the same period.
You do not have a record of what would happen without warming. All you have is a statistical guesstimate.
After reading the abstract and supporting information, I am still wondering the size of each instance of a record. Was it a single weather station, a grid cell or a part of a continent? There are no comparisons which would indicate the statistical size of each “record setting event”. If the event is half a continent, then that is more alarming than the results of individual weather stations. In fact statistically, wet/dry events from individual stations are not significant.
One graph does indicate that most of the data is from areas with high population densities. The Amazon basin had almost no data sources, but was included with coastal Brazil by infilling (I believe).
When I saw this …
“over the period 1980-2013”
I knew it was nothing but cherry picking. Was is sad is there are some people who think these paper are science.
If both were occuring in the same locations, it would be a different story. Shifts from one region to anothet are…well, “normal.”
It would be interesting to understand what would happen if a clean air act was introduced in China. Would the increased insolation in the east change the jetstream and hence the track of precipitation? Would the associated warming be attributed to CO2?
“if they do not agree on solutions to limit warming to well below 2 degrees, we’re headed for 3-4 degrees within this century. ”
Wow, that is catastrophic!
There can be no argument over that My poor grandchildren
Regards
M
The great flood of 1861-62 must be a fictitious event.
I find it difficult to believe they have accurate rainfall records going back a hundred years for most of Africa if they don’t even have proper temperature records. I suspect ‘modelling’.
In Sweden they said we would face severe flooding from increased precipitation due to more evaporation from the warming.
Then we had an unusual drought this Summer (I avoid using words like extreme or unprecedented) instead.
Since there was an election in November, the Greens then changed it to attribute all “extreme weather” to global warming. Including drought.
Some more honest scientists admitted they were surprised.
Then they said this was “the worst drought since 1955”.
Which made me think they just admitted it has nothing to do with CO2 then – or why was it so much dryer in 1955?
They were almost voted out of parliament, so people are on to them I guess.
The media, however, is not.
Here in Aus we, apparently, have had two 100 year wet events in the last few weeks. It has been wet, thanks to to Tim Flannery, who predicted there would be no more rain.
Bigger or more frequent episodes of heavy rain are to be expected with global warming. I think it is commonly agreed that this will put more water vapour into the atmosphere, which will make for greater precipitation. However, this will come with less draught. Which is why the Sahara was green 7000 years ago, and why it has always been bigger during glaciations and smaller during interglacials. Those that tell that we will have both more extreme rains and also more terrible draughts are lying, and the data does not support what they claim.
That is the most severe case of near sightedness, reported as something new, that I have ever seen! It’s like they don’t even know ice cores exist. Of course climate has extremes now and then. If it didn’t, studying ice cores would be the epitome of boring “boring”research!
Given how short the record is, and given how many places are monitored around the world. Just random variation would cause thousands of new records to be set every year.
Now there is a mind attuned to statistics!
Those PIKKIE experts telling us something NEW?
https://www.google.com/search?q=elbe+%C3%BCberschwemmung+2002&oq=elb%C3%9Cberschwemmung&aqs=chrome.