There is a misleading news article in the Fort Collins Coloradoan (h/t to Steve Geiger) that reads
Larimer County’s water supplies – and those of most of the state’s mountain counties – are at little risk of diminishing in the face of climate change because Northern Colorado could see more precipitation as the Earth warms, not less.
That conclusion was spelled out in a report issued Tuesday by California-based Tetra Tech and the Natural Resources Defense Council, which looked at climate change’s effects on water supplies across more than 1,500 counties nationwide.
Some of the most devastating effects on water supplies will be felt up and down the Great Plains, including Weld County and Denver, according to the report.
The authors of the report created a “Water Supply Sustainability Index,” which shows, county by county, the threats climate change pose to water supplies.
The report uses public water data and climate projections from the Intergovernmental Panel on Climate Change to show that 14 states face a high risk of having their water supplies diminish as temperatures rise and water demand exceeds availability by 2050.
Climate change might pose moderate to extreme risk to water supplies in Jackson, Mesa, Delta, Montrose, Montezuma, La Plata, Alamosa, Rio Grande, Moffat and Saguache counties in addition to those in the Eastern Plains, according to the report.
The study’s lead author, Tetra Tech principal engineer Sujoy Roy, said Tuesday that Colorado’s Eastern Plains are at high risk of seeing their water diminish by mid-century because of the region’s heavy use of groundwater, which could begin to dry up.
Groundwater use for agriculture in the Great Plains, Texas and the Southwest already exceeds water supply, according to the report.
Roy said a region’s risk of seeing its water supplies disappear with the advent of climate change depends on how much it relies on stored water during the summer. If water demand exceeds what’s falling from the sky or flowing down from the mountains, the higher the risk of diminishing water supplies.
Larimer County is expected to see more precipitation as temperatures rise, lowering the risk to the county’s water supplies, Roy said.
This article perpetuates the scientifically unsupported claim that there is skill in predicting regional climate decades into the future. Kevin Trenberth, one of the IPCC authors wrote in 2007 (Predictions of climate)
“However, the science is not done because we do not have reliable or regional predictions of climate.”
We need regional predictive if droughts decades into the future are going to be correctly forecast, as is claimed in this news article. However, this level of forecast skill does not exist.
Policymakers are being lulled into a false sense of confidence that we understand where water resource threats exits and where they do not. The reality is that natural climate variations have produced multi-decadal droughts in the past (e.g. see) even without human intervention into the climate system. The adoption of a bottom-up resource-based vulnerability perspective (see) is a much more robust approach for policymakers to apply than the use of the top-down IPCC predictions.