Having issued that warning, I was privy to another discussion in a closed list, and once more amazed at the misunderstanding of the original thesis and subsequent events within the scientific community as well as in the public mind.
The evidence for global warming did not come (never came) from climate models alone. So rebuttals to global climate change based on the flaws of models misses the point. The evidence comes from multiple sources.
1. The geological record of past climate and its relationship to various atmospheric conditions. This research really began in the 1950s, when serious work with ice cores and pollen analysis, tree-ring data, and radiocarbon dating (less accurate but with a longer range) gave the first substantive links between physical and biological evidence of paleoclimates. The International Geophysical Year (1957) gave a big push to such research, but some had begun before then. In other words, through the 1950s, '60s, and '70s, and continuing to the present, increased data, increased refinement of research methods, and direct advancements in research methods, allowed scientists to correlate climate to atmospheric gas composition.
2. Geophysical evidence in the present day includes the rapid melting of glaciers and ice sheets and rising sea levels, rising global sea temperatures and global mean temperature, etc.; geochemical evidence includes higher carbon dioxide content of the air and increasing acidification of sea and fresh water.
3. Meteorological evidence includes poleward shifting of dates of first frost, increased variability in seasonal temperatures and rainfall, increased variability in seasonal fluctuations of high-altitude winds (jet streams), etc.
4. Biological evidence includes the poleward migration of cold-intolerant plant species, poleward migration of cold-intolerant vertebrate and invertebrate species both in the oceans and on land, increasing desertification of semi-desert regions, winter survival of pest species formerly killed off by hard freezes. In the Arctic, melting of permafrost has already begun on the flanks of melting glaciers, with release of additional greenhouse gases from the decay of long-frozen plant materials, only some of which carbon dioxide is used by the new plant cover. A mismatch between migratory species and their food sources due to changes in temperature and rainfall that affect both plants and insects has been demonstrated in Europe and North America.
Contemporary changes are readily observable and have increased in the past 30 years. Some of them I have personally observed: semi-tropical plants migrating two "planting zones" north, changes in migration patterns and the mismatch of food source to migrant, milder winters in the past 10 years v. the previous 30, changes in rainfall patterns with a shift of jet streams to the north, etc.
To argue that these changes--predicted by the original hypothesis--are not caused by global warming would require an alternative explanation. So far, no anti-climate-change enthusiast has offered such an explanation.