Looks Like Rain Again: Rain, Climate Change and Alaska


One of the predicted effects of anthropomorphic climate change is more heavy downpours of rain. As Interior Alaska wades through the rainiest June in history and is on track for the rainiest summer ever, maybe we should look at the data.

Figure 2.18: The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and end points of the trends for 1958 to 2012. (Figure source: updated from Karl et al. 2009).

Figure 2.18: The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and end points of the trends for 1958 to 2012. (Figure source: updated from Karl et al. 2009)

The graphic is taken from the National Climate Assessment‘s website. The basics are simple. More CO2 means warmer air. Warmer air holds more water vapor. Billions of tons of more water vapor. That water vapor has to come out as precipitation. The only question for science is whether it comes out in heavier rainstorms – deluges – or as more steady rain.

The computer models have suggested for some years that the result would be deluges. And that’s what’s being observed in the field. Increasing numbers of extreme events. Alaska has seen an 11% increase in extreme precipitation events from 1958 to 2012. As CO2 is pumped into the air, the number and frequency of these events will increase. The computer models show the impact of these severe precipitation events falling most heavily (sorry) on Alaska.

Figure 2.19: Maps show the increase in frequency of extreme daily precipitation events (a daily amount that now occurs once in 20 years) by the later part of this century (2081-2100) compared to the later part of last century (1981-2000). Such extreme events are projected to occur more frequently everywhere in the United States. Under the rapid emissions reduction scenario (RCP 2.6), these events would occur nearly twice as often. For the scenario assuming continued increases in emissions (RCP 8.5), these events would occur up to five times as often. (Figure source: NOAA NCDC / CICS-NC).

Figure 2.19: Maps show the increase in frequency of extreme daily precipitation events (a daily amount that now occurs once in 20 years) by the later part of this century (2081-2100) compared to the later part of last century (1981-2000). Such extreme events are projected to occur more frequently everywhere in the United States. Under the rapid emissions reduction scenario (RCP 2.6), these events would occur nearly twice as often. For the scenario assuming continued increases in emissions (RCP 8.5), these events would occur up to five times as often. (Figure source: NOAA NCDC / CICS-NC).

What does a five-fold increase in extreme precipitation events mean? That a 100 year flood event like 1967 will become a 20 year event; that a 500 year flood event will become a 100 year flood event. Our infrastructure isn’t designed for the changes that are coming. Dikes are not high enough. Dams aren’t big enough. Simple issues like culverts not being big enough, resulting in road washouts.

When you look at this summer’s experience in Fairbanks it’s increasingly apparent that this is the future; the kinds of record-setting rainfall events in June and so far in July are the new normal.

You should read the whole report. You should make an effort to get climate change deniers like Rep. Don Young (R, Senility) to read the report. We can either get about the business of reducing CO2 emissions or brace ourselves for a whole lot of precipitation.

 

 

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