In past posts I have been critical of California policy makers who are using unvalidated climate change models to make polices with long term economic impacts. Some of these models have been around for over 20 years and billions of dollars spent to improve their forecasting skill, yet they fail some simple tests. Dr Roger Pielke has published a climate model test that even our local lefties can understand.
According to Dr Pielke there are two necessary requirements for multi-decadal global climate models must meet before multi-decadal projections for the coming decades should be communicated to stakeholders and policymakers.
In terms of testing the models, necessary conditions (but still not a sufficient condition) for the models to have any credibility to predict the future climate on decadal time scales are:
1. They must accurately simulate (hindcast) the statistics of major atmospheric and ocean circulation features over the last few decades (since real world data is available)
2. They must accurately simulate (hindcast) the statistics of the changes in the statistics of these major atmospheric and ocean circulation features over the last few decades.
If they cannot do both #1 and #2, they must be rejected as robust predictive (projection) tools for the coming decades.
A rationalization that the climate forcing in the coming decades could be outside of what has occurred in the past does not in any way remedy this deficiency. If they cannot skillfully predict #1 and #2, model predictions of the coming decades, published in journal articles, news reports, and climate assessments, are misinforming and misleading stakeholders and policymakers.
That seems very clear to me. If a climate model cannot predict the climate we know about, how can we predict the future climate change 20, 30, 50 years into the future?
I am outraged that CARB and other California Agencies are using climate models that cannot meet tests #1 and #2 to make policies that are costing tax payers billions of dollars and in fact can endanger millions living in the state. These agencies have used multi-decadal projections of global warming, when there is a much higher probability that we are on the cusp of another Grand Minimum, like the Dalton Minimum and Maunder Minimum.
It was during these minimum periods that California experienced some of the longest droughts. During the Dalton Minimum there was a 13 year drought according to the mission records, nothing like the 3-4 year droughts we experience with the coming and going of El Niños and La Niñas, which are cyclical and much in evidence in the current climate record. While we do not have a CA climate record for the Maunder, we do have one from China: Northern China experienced droughts lasting 15 years (1628-43). The resulting famines led to an extensive breakdown of social order and a large number of peasant rebellions. The Droughts of multi-year durations that dominated northern China during 1628-1644, were associated with the low solar activity and cold conditions of the Maunder Minimum.
During during the Medieval Warm Period, which lasted from about AD 950–1250 we had droughts in the Sierra lasting 200 years:
During the last 500 years, a wet climate, punctuated by intermittent but substantial droughts, began to dominate the region, and lake levels again rose and cirques glaciers reformed in the Sierra. A series of substantial droughts are documented during this period, however. Dozens of submerged tree stumps are located up to 300 feet below the present day level of Donner Lake a tributary of the Truckee River; carbon –14 samples from one stump date from AD 1433 (Lindstrom and Bloomer 1994). Another warm period, documented by tree-ring studies and Truckee River run-off, dated between AD 1579-1585, and again around AD 1630 (Hardman and Reil 1936). It is possible that Lake Tahoe contributed relatively little water to the Truckee River during the last 200 years. During the century between the mid 1700s to mid 1800s, the level of Lake Tahoe may have been below its rim, with no water flow into the Truckee River. This is documented by a submerged stump in the Upper Truckee River Delta dating from AD 1720 (Lindstrom 1996a), one from Donner Lake dating from AD 1800 (Lindstrom and Bloomer 1994) and one in Emerald Bay dating to AD 1840 (Lindstrom 1992). The 40 years between AD 1875-1915 were the longest period during which the flow of the Truckee River was above the average. During the AD 1930s drought, Lake Tahoe ceased to flow from its outlet for six consecutive years. Drought within the last decade (late 1980s to 1990s) either stopped Tahoe’s flow into the Truckee or reduced it to almost nothing.
The multi-decadal projections do not address these cool dry periods when drought was dominate. California should be building dams, not flood control levees. Dams store water for use by humans and can be used to moderate floods by capturing water. The focus on global warming, rather than our climate history is putting million in the state at risk. Call your Assemblyman and State Senators and demand that California Agencies only use computer models that can test #1 and #2.