Over the last few decades, the public question of climate change has shifted from being a scientific question to being a political question. Because the existing temperature data is very strong, an increasing number of people currently believe that the climate is becoming warmer. In response, most polls from the past year have shifted from questioning global warming to asking about the cause of global warming: solar activity, cosmic rays or other extraterrestrial sources, greenhouse gas levels (anthropogenic or as a result of natural Earth cycles), or some combination of these.
However, many people still think that the average temperature of the Earth is not increasing at all, and some of them believe that global warming is a complete hoax. They do have several rational reasons for this, as well as some "common sense" reasons.
Until the late 1970s, popular science magazines and newspaper science sections were filled with news of the coming ice age. For most of the U.S., 1977 was a winter for the history books. In fact, there was a slight downward movement of temperatures between the 1940s and the 1970s, which has now been traced to an increase in sulphur in the air due to increased coal burning.
However, the temperature glitch also led to several scientific studies which speculated that the cooling trend could lead into a new ice age. Roughly 10% of the climate studies of this time examined this possibility. The other 90% were already predicting the greenhouse effect as early as 1968.
Time Magazine was cautious in its coverage of the possible ice age, staing that "some scientists ... think that the cooling trend may be only temporary." However, Newsweek jumped on the story with speculative extremes which were not sourced in the studies of the time. In fact, Newsweek went so far as to claim, inaccurately, that "the evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it."
Newsweek printed a retraction on October 23, 2006. However, this retraction is seen by diehards as part of the Great Global Warming Conspiracy.
Most current media coverage has been so careful to show both sides of the climate change issue that it did not mention that the sides were not equally represented. In particular, the opinions of scientists were weighted equally on the basis of their science degree, regardless of whether any particular scientist was qualified as a climatologist or not.
Much is sometimes made of a petition, which states that there is "no convincing scientific evidence" of anthropogenic global warming, which has been signed by over 31,000 scientists. However, according to the site itself, just 39 of those 31,000 signers have educational specialties in climatology. The petition does not give information about whether those 39 signers had more than a bachelor's degree, which is the minimum required for signing. The vast majority of signers had completely unrelated scientific degrees, most of them in technological fields or even in basic science. The sample petition card shown on the main page belongs to a person with a PhD in physics, which does not give any authoritative qualification for the information stated by the petition.
In particular, meteorologists have often been used to oppose climatologists. As of the time of writing, 343 meteorologists had signed the petition, or close to 1% of the total number of signatories. Until quite recently, most meteorologists did not believe in climate change at all. It has only been much more recently that a majority of meteorologists now believe in climate change, although there is still strong disagreement over the cause.
There is certainly a great deal of money to be made from all sides of the global warming issue. The speaking fees and investments of Al Gore have dominated the right-wing press, but that only represents about $18 million of the trillions of dollars that have been invested, paid for, or extracted from all sides of the global warming issue.
By way of scale, British Petroleum's profits are apparently so high that it barely blinked at the $7.8 billion estimated payout to those who were affected by the Deepwater Horizon disaster. It would be rational for a company to want to maintain that level of profit. Because public belief in anthropogenic global warming could cut into that profit, most large oil companies invest heavily in anti-anthropogenic messages. These messages are conveyed to policy makers and friendly media through lobbyists, lawsuits, and sponsored think tanks.
The primary message from these sources used to be that climate change did not exist. Now, the primary message is that climate change is not anthropogenic. Logically, if climate change is not caused by people, then people don't have to change what they are doing. Business and profits can continue as usual, and people don't have to sacrifice any creature comforts.
The ongoing economic crisis has added an extra layer onto that message. Many people who think global warming is a hoax also think that any changes to limit carbon release will also increase unemployment and harm the economy.
Common sense demands that all claims should be measured against personal experience. During the 1970s, when the weather was cold and getting colder, common sense argues against global warming. Some places are still enduring unseasonable cold. On the eve of the Olympics, London, England is among them. If a person has to dig out from a number of historic blizzards, it is hard to believe that the Earth is warming up.
On the other hand, common sense says something completely different after a non-existent winter and an unrelenting heat wave. The global change models have never stated that global warming would affect all areas equally and evenly.