I'm not asking for arguments about whether global warming is true. I'm asking why denying the presence of global warming is primarily associated with a conservative political affiliation.
I am looking for judgment-free answers.
I think it's from a combination of factors.
The following is the perspective from the United States:
Conservatives are, on the whole, more aligned with business and/or industry
Since industry is most likely to be adversely affected by the consequences of regulations to reduce global warming (emissions restrictions, for example) there is an incentive to deny global warming.
Conservatives are, on the whole, more skeptical of environmental causes
This goes back a long time. Modern examples include use in some conservative media of "Sierra Club" as a slur or insult.
Conservatives are more skeptical of science, especially science backed/funded by Universities and/or the government
This also goes back a long time. From evolution to climate change to stem cell research to gun violence research to homosexuality, conservatives are distrustful of science, especially "new" science. This makes sense since conservatism, at its core, is avoiding change for change's sake and preserving core values. Skepticism of change (whether scientific or not) is to be expected.
The particular skepticism of government/University research stems from a perceived liberal bias in universities and a political bias in government institutions.
Most of the advocates for action on climate change are liberal
Notable here are people like Al Gore. Having someone like Gore as a figurehead for a movement will guarantee a certain amount of opposition. This would be the same as say Dick Cheney endorsing something - a percentage of liberals will oppose it just because Cheney is for it.
The likely reaction to climate change (regulation) goes against libertarian ideals
Not all conservatives are libertarians, but libertarians in general align more with conservatives mainly on economic issues, and reducing government regulation is a big piece of this. There's no way to reduce global warming without increased regulation and increased size of government.
Judgement-free answers might be difficult, given that it's a partisan subject to begin with.
That said, in general - in the United States, at least - the issue isn't so much about denying global warming as much as it is about protecting and favoring the major fossil fuel industries:
On a broader level, it's also about promoting deregulation.
The politicians who promote the concept of "Catastrophic Anthropogenic Global Warming" have also promoted the following measures:
Most conservatives are in favor of small government. They tend to oppose higher taxes. They tend to demand strong reasons (such as "it is necessary to win this war", or "it causes brain damage", or "it risks eternal damnation") before agreeing with government intrusions into people's lives. They also expect these "strong reasons" to either be obvious to the common man, or scriptural. Thus, they have many reasons to be skeptical of "Catastrophic Anthropogenic Global Warming".
Libertarians often argue that people should be free to risk "brain damage" by using drugs -- but "brain damage" undercuts the libertarian argument that people tend to choose wisely or rationally. "Eternal damnation" is a religious argument -- but many people sincerely believe that no pleasure "in this world" is worth "eternal damnation".
By the way, any competent historian knows about "Global Warming" -- 200 years ago, the Hudson and the Thames froze regularly. They stopped doing so even before people started burning huge amounts of coal in the late 19th century. Most conservatives recognize a modest amount of "Anthropogenic Global Warming". They just doubt the "Catastrophic" part. Simple models suggest that doubling the CO2 concentration in the atmosphere could cause average atmospheric temperatures to rise by about a degree. More complicated feedback-response models that use a lumped feedback parameter suggest that the same doubling could cause average atmospheric temperatures to rise by less than 2 F°. This is a modest change; many places in the world have daily swings of 30 F°, plus another 50 F° of seasonal variation. 1,000 feet of elevation change corresponds to about 2 - 5 F° of temperature change. The end of an ice age is associated with about 10 - 20 F° of temperature rise, according to interpretations of the Vostok ice cores.
In summary, the measures proposed by proponents of "Catastrophic Anthropogenic Global Warming" are "you bet your country" type measures, and measures that intrude into the daily lives of most ordinary people. Conservatives demand solid evidence of the "Catastrophic" part before they will agree with such measures.
I am not claiming that the following is the main reason, why conservatives deny climate change, but it certainly plays into it:
One central reaction to climate change (and environmental issues in general) is to change our behaviour (i.e., using less fuel, electrical energy, eating less meat, …). And though conservativism is mainly about opposing change of social aspects, it should not surprise that it attracts people who oppose change on a more general level. And since nobody would admit (even to himself) that he opposes change for its own sake, any reason is welcome.
Feel free to include this answer into the existing ones …
Conservatives believe that government should do less. The scientists who say "the earth is heating up" always seem to say "...and that means that government should do more to prevent heat-related problems."
Since conservatives believe that government should do less, their reactions to these scientists will include all of the following:
Also, since conservatives control government spending in science right now, there is a conservative movement toward studying climate smarter not harder by increasing investment in satellites, deep ocean probes, and other ways of getting a better monitor on the earth's heat balance than is presently available. This effort can shrink those pesky error bars and bring both sides to an agreement better than agreeing to pave the entire Mojave Desert with mirrors or to junk each and every existing combustion-based engine block in the US.
Among other reasons:
Conservative think tanks, conservative media, corporations, and industry associations (especially for the fossil fuels industry) -- domains dominated by conservative white males -- have spearheaded the attacks on climate science and policy from the late 1980s to the present," McCright and Dunlap concluded in their study. "The results presented here show that conservative white males in the general public have become a very receptive audience for these efforts.
Let me add the following to JNK's excellent answer. There are remedies for global warming that could in principle work well for conservatives e.g. like nuclear energy that however in today's world require massive investments and are therefore not such attractive options.
Until the mid 1980s there existed a strong push to get to a carbon-free energy infrastructure based on nuclear energy. This was not motivated by global warming, rather the finiteness of the fossil fuel reserves compared to nuclear energy. By using breeder reactors to convert U-238 to fissile Pu-239 and Th-232 to fissile U-233 the known reserves can power the world for the next 30,000 years compared to just a few centuries when using only fossil fuels or when using only ordinary nuclear reactors using U-235.
Due to public opposition to nuclear energy, too few new nuclear power plants were build to make breeder reactors economically viable. The Integral fast reactor was canceled as a result, and the SNR-300 in Germany never became operational after completion.
Then with nuclear energy today not representing a large industrial base compared to the fossil fuel industry, conservative politicians will be more inclined to downplay the problems with using fossil fuels.
This should perhaps be a comment rather than an answer, but it will be too long by far for a comment, so...
I see that there is contention around the idea that there is an association between "conservatives" and climate change denial. It seems that many Republican voters do not deny climate change, and that some Democratic voters do.
But the association cannot be reduced to "how many Republicans deny climate change"; it has to consider "how many climate change deniers identify as Republican". I don't have statistics at hand, but apparently Democrats that don't "believe in climate change" are rather apathetic about the issue, while there is a sizeable minority among Republicans that not only "disbelieves in climate change", but further believes that "climate change is a lie or a conspiracy". Such phenomenon does not seem to plague the Democrats.
However, what is commonly called "conservative" in the United States doesn't seem to me compatible with the traditional definition of "conservative". In this question, If conservatism believes in individualism, then why do conservatives often support regulation of personal decisions?, indigochild's answer reminded us that "At its core, conservatism is an anti-utopian philosophy". In a comment to that answer, I pondered that "While I tend to agree, I would remark that this rules out a huge part of self-styled American conservatism. Some of the "conservative" tendencies in the US - and certainly those that consider themselves most conservative, or more radically conservative, and are generally considered as such by the general public discourse - are extremely utopian. Following your reasoning, such tendencies would be better described as far right liberalism rather than conservatism".
I think that this distinction stands here. "True conservatives", if there is such a thing, would be anti-industrialisation, or at least very cautious about industrialisation, and as such would probably take the climate change issue as a reminder that unchecked progress is folly, that tampering too much with nature is hybris, and that we should not mess (too much, at least) with our planet, given that we do not have any alternative one at hand.
The reason that "denying global warming is associated with a Conservative cause" is because it's a convenient lie used as a political attack ad on conservatives, strongly propagated by liberals and their allies in US mass media.
In reality, it's a false association, as are most arguments made to "explain" it by liberals:
Only 13% more conservatives than liberals don't believe in global warming (83% vs 70%) if you use US party membership as the best available approximation.
Source: The AP-GfK poll conducted Nov. 29-Dec. 3 2012, by GfK Roper Public Affairs and Corporate Communications. It involved landline and cellphone interviews with 1,002 adults nationwide. Results for the full sample have a margin of error of plus or minus 3.9 percentage points; the margin of error is larger for subgroups.
The discrepancy is even smaller if you go outside USA, but you start running into issues of who or what "conservatives" are when you go global.
So, the main answer to your query is "there's no logical reason for global warming denying to be associated with conservatives, if you are willing to bypass partisan soundbites".
Moreover, GOP party platform explicitly acknowledges climate change:
“technology-driven, market-based solutions that will decrease emissions, reduce excess greenhouse gases in the atmosphere, increase energy efficiency, mitigate the impact of climate change where it occurs, and maximize any ancillary benefits climate change might offer for the economy.”
Let's look at last two Republican Presidential candidates.
Mitt Romney (2012) said the following in his 2012 book "No Apology":
It's impossible not to take a look at our current energy policies without considering the question of climate change. I believe that climate change is occurring -- the reduction in the size of global ice caps is hard to ignore. I also believe that human activity is a contributing factor.
John McCain (2008) was one of the first Senators to champion Cap-and-trade legislation. I won't bother hunting for quotes, but this NBC News article on the topic covers tons of details on McCains views.