This group brings together the best thinkers on energy and climate. Join us for smart, insightful posts and conversations about where the energy industry is and where it is going.

Post

We Just Had Five 1,000-Year Floods in Less than a Year. What's Going On?

Shira Silver's picture

Climate news and commentary blog for the Environmental Defense Fund (EDF).

  • Member since 2018
  • 91 items added with 34,172 views
  • Sep 8, 2016 11:00 am GMT
  • 439 views

Your access to Member Features is limited.

A 1,000-year flood is supposed to be extremely rare. Its chance of occurring in a given year: 0.1 percent.

So how do we explain that in the span of just five months, the United States logged no fewer than four deadly 1,000-year floods in states as widespread as Texas, West Virginia, Maryland and Louisiana – following a 1,000-year-flood that ravaged South Carolina last October.

It appears that the calculation of a 1,000-year event may no longer be the most accurate statistic. It was based, as are our increasingly common 100-year natural disaster events, on data from the past. We may, in other words, already have shifted so far into a new climate regime that probabilities have been turned on their head.

Climate change “supercharges” normal weather

Like any climate scientist will tell you, there is more to the story than what you see on the surface.

All climate and weather events are influenced to some degree by both natural climate variations and human-made climate change. The amount that each of these influences can exert on a particular event can theoretically range from 0 to 100 percent.

Rigorous scientific analysis has found that the extreme rainfall that caused a Texas flooding in May of 2015, for example, was caused by a fairly typical rainfall pattern associated with that year’s El Niño, a naturally occurring climate cycle, which had been supercharged by human-made climate change.

Working in tandem, these two phenomena together produced one of the largest multi-day flooding events Texas has ever experienced.

Recent floods continue the trend

But what about more recent floods like the one in Baton Rouge or Ellicott City, Maryland?

Attributing short-term extreme weather events to climate change is not a trivial exercise, even as the science of climate attribution has advanced rapidly over the last decade.

Using high-powered models and complex statistical analysisof observations, credible scientific statements can now be made about how climate change affect the frequency or intensity of a specific weather event.

There is an inevitable time delay between the occurrence of an event and the complete dissection of its various causes. This is why we cannot yet say with certainty that last month’s flooding in Baton Rouge, or the flash flood that devastated Ellicott City in July, were due to climate change.

71% more heavy rain since the 1950s

If you’re anything like me you don’t enjoy waiting for answers. So while it’s certainly wise to await the scientific analysis that is sure to be coming down the pike, we can still think about these events in the climate change context.

We know that as the global average temperature rises, more water evaporates from the oceans. This, in turn, increases the amount of atmospheric moisture that is available for storms to process into rainfall.

Increases in heavy downpours by region 1958-2012. Source: NCA

In fact, observations over the last 60 years indicate that over the United States, the amount of water falling in heavy rain events has increased substantially, and an astonishing 71 percent over portions of the mid-Atlantic and northeastern U.S.

In other words, if there were two storms with an identical structure over Boston, Massachusetts – one in 1955 and one in 2016 – the one in 2016 would, on average, produce 71 percent more rainfall.

Bottom line is that the heavy rainfall and disastrous flooding events that we continue to experience are certainly consistent with what the science tells us about the impacts from increasing global temperatures.

These floods are another reminder that we must change that trajectory.

By Scott Weaver

Photo source: Flickr

Shira Silver's picture
Thank Shira for the Post!
Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.
More posts from this member
Discussions
Spell checking: Press the CTRL or COMMAND key then click on the underlined misspelled word.
greggerritt greggerritt's picture
greggerritt greggerritt on Sep 8, 2016

This is really important, but American politics has becomea fact free zone. Facts and Science matter, but the right wing crazies have never seen a fact they liked, so they rule them out

Engineer- Poet's picture
Engineer- Poet on Sep 8, 2016

The right likes plenty of facts, but the left labels them “racist” and “intolerant”.

Bob Meinetz's picture
Bob Meinetz on Sep 10, 2016

Facts and science support nuclear (at least all the smart people say so), but if I recall correctly, you don’t.

There are nutcases on both sides of the fence.

Mark Heslep's picture
Mark Heslep on Sep 15, 2016

There are many areas where a climate change signal is strongly detected, especially global trends like temperature anomaly. Attribution of specific events is not one of them.
IPCC AR5 SREX, Chapter 4:

The statement about the absence of trends in impacts attributable
to natural or anthropogenic climate change holds for tropical and
extratropical storms and tornados …The absence of an attributable climate change signal in losses also holds for flood losses

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »