At a news conference announcing that 2015 broke all previous heat records by a wide margin, one journalist started a question with “If this trend continues…” The response by the Director of NASA’s Goddard Institute for Space Studies, Gavin Schmidt, summed up the physics of climate change succinctly: “It’s not a question of if…”

Even if global emissions begin to decline, as now appears possible after the agreement signed in Paris last December, there is no reasonable scientific doubt that the upward trends in global temperature, sea levels, and extreme weather events will continue for quite some time.

Politically and ideologically motivated denial will nonetheless continue for a little while longer, until it ceases to be politically opportune.

So how does one deny that climate change is upon us and that 2015 was by far the hottest year on record? What misinformation will be disseminated to confuse the public?

Research has identified several telltale signs that differentiate denial from scepticism, whether it is denial of the link between smoking and lung cancer or between CO 2 emissions and climate change.

One technique of denial involves “cherry-picking”, best described as wilfully ignoring a mountain of inconvenient evidence in favour of a small molehill that serves a desired purpose. Cherry-picking is already in full swing in response to the record-breaking temperatures of 2015.

Political operatives such as James Taylor of the Heartland Institute – which once compared acceptance of the science of climate change to the Unabomber in an ill-fated billboard campaign – have already denied 2015 set a record by pointing to satellite data, which ostensibly shows no warming for the last umpteen years and which purportedly relegates 2015 to third place.

Kevin Cowtan / RSS / Met Office HadCRUT4 , Author provided

So what about the satellite data?

If you cannot remember when you last checked the satellites to decide whether to go for a picnic, that’s probably because the satellites don’t actually measure temperature. Instead, they measure the microwave emissions of oxygen molecules in very broad bands of the atmosphere, for example ranging from the surface to about 18km above the earth. Those microwave soundings are converted into estimates of temperature using highly-complex models. Different teams of researchers use different models and they come up with fairly different answers, although they all agree that there has been ongoing warming since records began in 1979.

There is nothing wrong with using models, such as those required to interpret satellite data, for their intended purpose – namely to detect a trend in temperatures at high altitudes, far away from the surface where we grow our crops and make decisions about picnics.

But to use high-altitude data with its large uncertainties to determine whether 2015 is the hottest year on record is like trying to determine whether it’s safe to cross the road by firmly shutting your eyes and ears and then standing on your head to detect passing vehicles from their seismic vibrations. Yes, a big truck might be detectable that way, but most of us would rather just have a look and see whether it’s safe to cross the road.

And if you just look at the surface-based climate data with your own eyes, then you will see that NASA, the US NOAA, the UK Met Office, the Berkeley Earth group, the Japan Meteorological Agency, and many other researchers around the world, all independently arrived at one consistent and certain end result – namely that 2015 was by far the hottest year globally since records began more than a century ago.

Enter denial strategy two: that if every scientific agency around the world agrees on global warming, they must be engaging in a conspiracy! Far from being an incidental ornament, conspiratorial thinking is central to denial. When a scientific fact has been as thoroughly examined as global warming being caused by greenhouse gases or the link between HIV and AIDS, then no contrary position can claim much intellectual or scholarly respectability because it is so overwhelmingly at odds with the evidence.

That’s why politicians such as Republican Congressman Lamar Smith need to accuse the NOAA of having “altered the [climate] data to get the results they needed to advance this administration’s extreme climate change agenda”. If the evidence is against you, then it has to be manipulated by mysterious forces in pursuit of a nefarious agenda.

This is like saying that you shouldn’t cross the road by just looking because the several dozen optometrists who have independently attested to your 20/20 vision have manipulated the results because … World Government! Taxation! … and therefore you’d better stand on your head blindfolded with tinfoil.

So do the people who disseminate misinformation about climate actually believe what they are saying?

The question can be answered by considering the stock market. Investors decide on which stock to buy based on their best estimates of a company’s future potential. In other words, investors place an educated bet on a company’s future based on their constant reading of odds that are determined by myriad factors.

Investors put their money where their beliefs are.

Likewise, climate scientists put their money where their knowledge is: physicist Mark Boslough recently offered a $25,000 bet on future temperature increases. It has not been taken up. Nobel laureate Brian Schmidt similarly offered a bet to an Australian “skeptic” on climate change. It was not taken up.

People who deny climate science do not put their money where their mouth is. And when they very occasionally do, they lose.

This is not altogether surprising: in a recent peer-reviewed paper, with James Risbey as first author, we showed that wagering on global surface warming would have won a bet every year since 1970. We therefore suggested that denial may be “… largely posturing on the part of the contrarians. Bets against greenhouse warming are largely hopeless now and that is widely understood.”

So the cherry-picking and conspiracy-theorising will continue while it is politically opportune, but the people behind it won’t put their money where their mouth is. They probably know better.

Now read: The last time Earth was this hot hippos lived in Britain (that’s 130,000 years ago)