Global warming stopped six years ago. It might start again tomorrow, but from 2002 until now, average global temperatures have remained fairly constant. This is in contrast to the previous period when, as everyone knows, the temperature trend was upwards.

Most people I've mentioned this to were not aware of it. They assumed that temperatures had continued to rise in line with greenhouse gas emissions, which have certainly continued to increase. So it's worth looking at what's happened.

The two most prominent organisations that record global average temperatures are the British Met Office's Hadley Centre and America's National Climatic Data Centre. Their records might be called "official"- Hadley, for instance, is closely involved with the Intergovernmental Panel on Climate Change. Their records for temperature change can be found at their websites.

The usual chorus of environmentalists and editorial writers has chimed in to attack President Bush's recent speech on climate change. In his address of April 23, he put forth a goal of stopping the growth of U.S. greenhouse gas emissions by the year 2025.

"Way too little and way too late," runs the refrain, followed by the claim that nothing less than an 80% reduction in emissions by the year 2050 will suffice – what I call the "80 by 50" target. Both Hillary Clinton and Barack Obama have endorsed it. John McCain is not far behind, calling for a 65% reduction.

We all ought to reflect on what an 80% reduction of greenhouse gas emissions by the year 2050 really means. When we do, it becomes clear that the president's target has one overwhelming virtue: Assuming emissions curbs are even necessary, his goal is at least realistic.

The same cannot be said for the carbon emissions targets espoused by the three presidential candidates and environmentalists. Indeed, these targets would send us back to emissions levels last witnessed when the cotton gin was in daily use.

A couple of days ago, AT focused attention on the possible climate effects of sunspots, as solar cycle 23 runs longer than forecast, in Sunspots and a Possible New Ice Age . There are various measurements that scientists, as well as the curious, are looking at and updating almost daily, such as the length of cycle 23, number of days with no sunspots, and the official start of cycle 24.

All of it is interesting, though not very well understood.  In some circles there is a theory, increasingly backed up by data, that this extended duration and low magnitude cycle 23 is the reason for recent cooling, and that we may be in store for more cooling, maybe much more.

The Anthropogenic Global Warming (AGW) controversy has exposed much information, old and new.  One of the more interesting papers I have seen recently was written in the year 1999, and has to do with barycentric analysis (celestial mechanics) of the solar system and its possible effects on the solar cycle. In some scientific circles celestial mechanics has already been "ruled out, even disparaged as "astrology."

The Earth’s warming since 1850 totals about 0.7 degrees C. Most of this occurred before 1940.

The cause: a long, moderate 1,500-year climate cycle first discovered in the Greenland ice cores in 1983. The cycle abruptly raises our temperature 1 to 3 degrees C above the mean for centuries at a time--as it did during the Roman Warming (200 BC to 600 AD) and Medieval Warming (950 to1300 AD).

Between warmings, Earth’s temperatures shift abruptly lower by 1 to 3 degrees C--as they did during the 550 years of the Little Ice Age, which ended in 1850. The ice cores and seabed fossils show 600 of these 1,500-year cycles, extending back at least 1 million years.