When global warming alarmists condemn skeptics as “deniers,” that 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, the celebrated nineteenth century English biologist, explained, “Skepticism is the highest of duties; blind faith the one unpardonable sin.”
For more than 1,000 years, the world accepted Aristotle’s claim 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 confirm the Earth rotated around the sun.
Today, we have the same opportunity to see whether the evidence fits a popular theory, on global warming this time, but we risk media “house arrest” if we do.
Yet there are many inconvenient facts that demand explanation.
Prior Warming Confirmed
For example, Chinese researchers recently examined their ancient historic records, which go back farther than in any other society. They found evidence of a warm period from the year 1 to about 240 AD (known in the West 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 Little Ice Age. This is not what we have been told to expect from the Modern Warming. China during the Roman and Medieval periods also had better crop production 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 taken from Tibet yield an annual record of the air temperatures when the ice was laid down. Pollen and organic matter in peat bogs, as well as sedimentary deposits in lake beds, provide further proxy evidence of climate and biosphere conditions.
From this evidence, the Chinese researchers concluded China’s warmest period during the past 2,000 years occurred around the year 100 AD. This aligns with Roman records of growing wine grapes in Britain during their occupation of that island in the first century–whereas Britain was unable to grow wine grapes from 1300 to 1950 because of too-cold temperatures. The Chinese researchers also learned trees respond to warmth and rainfall by growing more rapidly.
If China was warmer during the first century than today, we must ask what is so remarkable about today’s warming.
Ice cores from Greenland and Antarctica confirm the existence of a 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. Carbon in tree rings and beryllium in the ice likewise indicate 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 observations made since 1860. Henrik Svensmark of the Danish Space Research Institute found a 95 percent correlation between the sunspot numbers and the record of the Earth’s sea surface temperatures.
Svensmark recently demonstrated that cosmic rays, which vary with the sun’s radiance, influence the amount of low, wet clouds on the planet, which deflect heat back into outer space. These clouds amplify solar variations fourfold. At any given time, 20 percent of the Earth’s surface may be shaded by such clouds.
It’s conceivable 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 carbon dioxide 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 carbon dioxide emissions have been only a small factor in our small recent warming (a net 0.2º 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 1,500 Years.