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.

CO2 Increases Lag Temperature Increases

In Al Gore’s movie, the ice record from the Antarctic shows temperatures and atmospheric CO2 levels tracking closely together through the radical ups and downs of four Ice Ages. The movie implies that more CO2 in the air produces higher temperatures.

But we’ve recently done more refined ice studies, which show the temperatures changed about 800 years before the CO2 levels. More CO2 did not produce higher temperatures; instead, higher temperatures released more CO2 from the oceans into the atmosphere.

If the climate models’ original greenhouse predictions had been valid, the Earth’s temperatures would have risen several degrees more by now than they have. The Earth’s net warming since 1940 is a barely noticeable 0.2 degrees C, over 70 years. For the sake of argument, let’s give the alarmists credit for half of this, or 0.1 degree C.

Moreover, the Earth has experienced no discernible temperature increase since 1998, nearly nine years ago. Remember, too, that the atmosphere is approaching CO2 saturation–after which more CO2 will have no added climate forcing power.

Temperatures, Sunspots, Cosmic Rays

There is a 95 percent correlation between Earth’s temperatures and sunspots since 1860. There is virtually no correlation between our temperatures and CO2 in the atmosphere.

The sunspot number has recently dropped to zero. In the past, when sunspot numbers and our temperatures have diverged, the sunspots have been the leading indicator. The temperatures have soon shifted to follow. Does this mean that Earth’s temperatures will soon decline? History says yes.

How long will the global warming alarmists be able to sustain the public hysteria without strongly rising temperatures? This will be a key factor in the short-term future of climate warming legislation.

Henrik Svensmark of the Danish Space Research Institute says cosmic rays are the link between the sun’s variability and Earth’s temperatures. More or fewer cosmic rays, depending on the strength of the “solar wind,” seed more or fewer of the low, wet clouds that cool the Earth. Further experiments to document this impact are planned in Europe.

“There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gasses is causing, or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.” That statement comes from a petition signed by more than 19,000 American scientists, available online at a site hosted by the Oregon Institute for Science and Medicine at

Warming Cycles Are the Norm

The Earth has had eight warming cycles since the last Ice Age. Several of these were apparently warmer than today, based on the evidence of fossils and isotopes.

The Medieval Warming until recently was known as “the little climate optimum.” Human numbers increased with the long, stable growing seasons; there were fewer and milder storms; and there were fewer deadly disease epidemics. Bubonic plague attacked Europe during both the Dark Ages and the Little Ice Age.

No wild species have gone extinct due to higher temperatures during the “unprecedented warming” of the past century. All of the existing species have been through even stronger warmings in the past. We have not examined their coping strategies, preferring to demand instead that somehow the climate cycle be stopped.

Arctic ice area has hit a modern low in recent months, but this cannot be due to global warming because the Antarctic simultaneously has the most ice in modern times. The polar regions have their own climate cycles, which operate within the longer 1,500-year cycle.

Earth also has the North Atlantic Oscillation, the Pacific Decadal Oscillation, the El Niño cycle, and a 22.5-year sunspot-related cycle in Southern Hemisphere rainfall.

The new book Unstoppable Global Warming: Every 1,500 Years cites hundreds of peer-reviewed studies by more than 500 fully qualified scientists who found evidence that

1) a natural, moderate 1,500-year climate cycle has produced several global warmings similar to ours since the last Ice Age and/or

2) our Modern Warming is linked strongly to variations in the sun’s irradiance;

3) sea levels are failing to rise importantly;

4) our storms and droughts are becoming fewer and milder with this warming as they did during previous global warmings;

5) human deaths will be reduced with warming because cold kills far more people than heat; and

6) corals, trees, birds, mammals, and butterflies are adapting well to the routine reality of changing climate.

Despite being published in such journals such as Science, Nature, and Geophysical Review Letters, these scientists have gotten little media attention.

Dennis T. Avery is director of the Center for Global Food Issues at the Hudson Institute and co-author, with S. Fred Singer, of Unstoppable Global Warming: Every 1,500 Years.