Climate predictions discussed


Climate prediction uncertainties somewhat depend on uncertainties found in the predictive chemical, physical and social models, as discussed in several Intergovernmental Panel on Climate Change (IPCC) assessment reports.

The reports may be found online at the IPCC website:

The IPCC’s report, titled “Climate Change 2001,” contains a discussion by the Working Group I on the scientific basis; and its Section F is titled “The Projections of the Earth’s Future Climate.”

These comments were made in Section F-5: “For some other extreme phenomena, many of which may have important impacts on the environment and society, there is currently insufficient information to assess recent trends, and confidence in models and understanding is inadequate to make firm projections.

In particular, very small-scale phenomena such as thunderstorms, tornadoes, hail, and lightning are not simulated in global models.”

Comments that were made in Section F-5, Table 4, about “insufficient data,” “conflicting analyses,” and “uncertainty” collectively suggest that the science regarding Climate Change prediction modeling is apparently still under some debate.

The IPCC’s Third Assessment report states that coupled climate models do not simulate with reasonable accuracy clouds and some related hydrological processes (in particular those involving upper tropospheric humidity).

Problems in the simulation of clouds and upper tropospheric humidity, remain worrisome because the associated processes account for most of the uncertainty in climate model simulations of anthropogenic change.

Typical model grid resolutions apparently are currently between 1 and 5 degrees in latitude or longitude. One degree of latitude is approximately 69 miles; and one degree of longitude in the vicinity of Walla Walla is approximately 45 miles. Thus a single grid covering 1 degree of latitude and 1 degree of longitude in our area covers approximately 3,100 square miles; and a single 5 degree grid covers approximately 78,000 square miles.

As a frame of reference, the total Snake River drainage area upstream of Pasco is approximately 109,000 square miles.

A single model grid of 5 degrees latitude/longitude thus is averaging conditions over an area approaching the size of the entire Snake River Basin; which extends from Pasco to the Grand Tetons and which has a wide variation in simultaneously occurring physical conditions.

Gene Spangrude

Walla Wall


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