When global warming alarmists condemn skeptics as deniers, it is an unscientific and socially dangerous characterization. Skeptics are not the enemy. On the contrary, they are crucial to science because they help us search for truth.
Scientific theories exist to be verified or proven false. Thomas Huxley, a famous nineteenth-century English biologist, explained, “Skepticism is the highest of duties; blind faith the one unpardonable sin.”
For more than a thousand years, the world accepted Aristotle’s word that the sun moved around the Earth, that the Earth was the center of the universe. Then Galileo, in the sixteenth century, used the newly invented telescope to learn the Earth rotated around the sun.
Today, we have the same opportunity to see whether the evidence fits a popular theory, this time on global warming–but we risk media “house arrest” if we do.
Yet there are those inconvenient facts: Chinese researchers recently examined their ancient historic records, which go back farther in China than in any other society. They found evidence of a warm period from the years 1 to about 240 AD (known as the Roman Warming); a cold period (the Dark Ages) from 240 to 800 AD; a warming (the Medieval Optimum) from 800 to 1400; and the Little Ice Age from 1400 to about 1920.
The Chinese records indicate the warm periods had fewer and milder storms, and fewer droughts and floods than the cold Dark Ages and the Little Ice Age. This is not what we’ve been told to expect from the Modern Warming. China, during the Roman and Medieval periods, also had better crops and more prosperity than during the cold times.
The Chinese researchers also looked at modern proxy evidence of past temperatures.
- The oxygen isotopes in ice cores yield an annual record of the air temperatures when the ice was laid down. The researchers looked at two ice cores from Tibet.
- Trees respond to warmth and rainfall by growing more rapidly, and the Chinese researchers examined two tree ring records from China and one from nearby Japan.
- They included analysis of pollen and organic matter in a deep peat bog on the edge of the Tibetan Plateau.
- They examined sediment cores from two lake beds in Taiwan.
From this evidence, the Chinese researchers concluded China’s warmest period during the past 2000 years occurred around 100 AD. (See Bao Yang, et al., “General Characteristics of Temperature Variation in China During the Last Two Millennia,” Geophysical Research Letters, 10 (2002): 1029/2001GLO014485.) This aligns with Roman records of growing wine grapes in Britain during their occupation of that island in the first century–even though Britain was unable to grow wine grapes from 1300 to 1950 because of too-cold temperatures.
If China was warmer during the first century than today, what’s so remarkable about today’s warming?
In fact, the Greenland and Antarctic ice cores, brought up during the 1980s, confirm the existence of a long, moderate 1,500-year climate cycle (plus or minus 500 years) that has brought the planet more than 500 global warmings in the past million years. Seabed sediments, lake sediments, fossil pollen, cave stalagmites, and worldwide glacier movements all agree. Carbon14 in the tree rings and beryllium10 in the ice seem to confirm that the cycle is connected to variations in the sun’s radiance.
Perhaps the most powerful evidence of all is the strong correlation between sunspot records and the Earth’s temperatures during the “thermometer years” since 1860. Henrik Svensmark of the Danish Space Research Institute found a 95-percent correlation between the sunspot numbers and the lagged record of the Earth’s sea-surface temperatures.
Svensmark recently demonstrated that cosmic rays, which vary with the sun’s radiance, can create more or fewer of the low, wet clouds that act as the Earth’s thermostats by deflecting more or less heat back into outer space. Low, wet clouds amplify solar variations fourfold. At any given time, 20 percent of the Earth’s surface may be shaded by such clouds.
Svensmark could be looking at the wrong evidence. Or perhaps the global warming believers will discover some new and more powerful evidence of manmade warming. To date, however, the global warming advocates have only (1) the fact that the Earth is warming; and (2) a set of computerized global climate models that blame increasing CO2 for rising global temperatures.
The reality is, since 1998 CO2 levels have continued to soar while the Earth’s temperatures have held stable.
The climate models are not evidence; they are guesses. The fact that they tend to agree with each other says more about discussions among the modelers than about the accuracy of the models.
The Earth could be warming due to either natural or manmade causes, or both at the same time. But, the facts strongly suggest human CO2 has been only a small factor in our small recent warming (a net 0.2 degrees C since 1940). That isn’t denial; it’s reality.
Dennis T. Avery ( [email protected]) is a senior fellow with The Heartland Institute and coauthor of the bestselling book Unstoppable Global Warming Every 1500 Years.