Saturday, May 05, 2018

Intense rain, climate change, again..

It's long been a theme here that new records for intensity of rainfall and resultant flooding, due to even the relatively modest increase in the atmosphere's water carrying capacity is likely the first big problem with climate change in many parts of the world.

And it's a hard one to deal with:   sure, in theory, you can argue that flood prone cities can prepare themselves by spending more on higher capacity drainage systems.  But replacing pipes and drains of one diameter that used to be adequate 100 years ago with significantly larger drains to cope with the increased frequency of intense, overwhelming rainfall, is  surely going to be very expensive; and for a regional government it is not going to be clear which particular location is going to face an unexpected downpour first.

Why on earth should I think that the economic modelling of climate change effects could be accurately making estimates of that when tallying up the figures for their estimates of when the benefits of climate change crosses the line of being clearly outweighed by the harm?    I would think they can put a rough estimate of of the cost of increased damage from flooding - they've got some historical guidelines for that - but as flooding increases, governments will be under pressure to pre-empt them by the expensive sorts of capital works that I would think is very, very hard to estimate.

Anyway, these thoughts were inspired by the news of (what sounds like) a new rainfall record in Hawaii, which has caused lots of damage:
A staggering rainstorm on the north shore of the Hawaiian island of Kauai is the latest clue that climate change-related impacts are already threatening the islands. On April 14 and 15, a gauge in Waipa recorded 49 inches of rain in 24 hours. For perspective, the rains from Hurricane Harvey, which inundated the Houston area with up to 60 inches last year, occured over a four-day span.  

The state is still assessing the full extent of damage, and Gov. David Ige recently announced a plan to help farmers who suffered losses during the storm. More than 220 people had to be airlifted to safety by the Army and National Guard as a major road was blocked by landslides. A herd of bison was carried off by the flood waters, with some animals having to be rescued from the ocean.

A group within the National Oceanic and Atmospheric Administration that investigates extreme weather and climate events is analyzing the storm to  determine whether the storm broke the national record for the most rainfall within a 24-hour period.

The current 24-hour record  is 43 inches, set in Alvin, Texas in 1979.

Setting a new record will be just the latest reminder that as the climate warms,  parts of Hawaii are already experiencing bigger torrential rains and will likely see more frequent tropical cyclones. Pao-Shin Chu, Hawaii’s state climatologist and a professor at the University of Hawaii, noted that his research showed that the Big Island has seen more frequent heavy rains in the past 50 years.

“If given a one degree C warming, the atmospheric moisture is expected to increase by 7 percent. With this additional moisture available in the air, it may help trigger heavy downpours if other conditions are right,” Chu said by email.
Of course, the damage caused in a rural area is not even necessarily preventable by better drainage.   It can be hard to retain a hillside if it collapses.

Here's a recent article, too, from DW about extreme weather being validly linked to climate change is increasingly proved by science.  Interesting that it deals with the Roger Pielke Jr claim that that increased costs from weather events is more related to increased building in risk prone areas (and therefore not proof there are more extreme events causing damage.)   The insurance industry doesn't believe it; scientists don't believe it.   And Pielke Jr's continuing contrarianism is fading from influence, anyway.  Good.

No comments: