Some people bring joy wherever they go, some ... whenever they go. And I know which of these relates to climate sceptics and deniers, who have for years successfully managed to delay action on climate change.
If the world doesn't cut the pollution of heat-trapping gases, the already noticeable harms of climate change could spiral "out of control", Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC), warned this week.
As the authors of the IPCC's latest report put it, starkly: "It is a call for action". The Obama White House also says it is taking this new report as a call for action, with Secretary of State John Kerry saying, "The costs of inaction are catastrophic."
This report tells us that we have two clear choices: cut carbon emissions now, move to decarbonise our economies and invest in adaptation to a climate-changed world and have a world that has challenging and just barely manageable risks; or do nothing and face a world of devastating and unmanageable risks for millions of people.
However, the report also makes it clear that we still have time to act. And action is the key issue. We can limit climate instability and adapt to some of the changes we see now, but without immediate and specific action, we are in danger of going far beyond the limits of adaptation.
In other words, you fix the roof when it's sunny, when you have time – not when it starts rain heavily.
In the end, the only question that matters is: what are we going to do about it?
Perhaps this is one way to think about how to deal with climate sceptics. Put aside their scientific counterclaims and let's focus on their politics.
So what are the politics behind climate denial? Well, it turns out to be a rather potent brand of populist, right-wing conservatism, in which climate science and climate politics are part of a 'left-wing' conspiracy, or justification for greater state 'interference' with personal freedoms.
This turns out to be largely a defence of the free market, of unfettered capitalism, as can easily be seen by the right-wing credentials of well-known climate sceptics, such as Nigel Lawson, Bernard Monckton, or, more locally, former DUP minister Sammy Wilson, not one of whom has expertise in climate science, curiously enough, but are masters in the art of public rhetoric. Or from the contagion of well-funded right-wing 'think tanks', whose main job is to produce 'junk science' and provide media-friendly climate denial positions and speakers.
The political conservatism underpinning climate sceptics and deniers means that no amount of scientific facts, no increase in the number of scientists who agree that human beings burning fossil fuels are the main cause of climate change, will change their minds.
On the one hand, it is not so much to climate science that deniers reject, but the political and economic implications of action to adapt to a climate-changed world and action to reduce the causes of climate change. Namely, that we cannot continue to allow the unfettered free market to fry the planet, nor rampant consumerism to dominate our view of a decent human life.
On the other hand – and this seems to be the case from studies in America and Australia – for many climate sceptics "climate change" is not about the climate at all, but a cypher for a whole host of attitudes and policies that are objectionable from a conservative point of view.
These include – take your pick – the growing secularisation of society, marriage for gay people and demands for greater equality, including gender equality.
Social science research tells us climate scepticism is rooted in people's core values and worldviews. In short, people who believe in the fiction of the "invisible hand of the free market" are unlikely to be persuaded by ever more compelling scientific facts and peer-reviewed research.
They simply do not care about the science. Thinking even more scientific certainty will make them change their minds and get out of the way for those of us who wish to tackle the problem and secure a habitable planet for the future is like being in a foreign country and naively thinking speaking English in a louder voice will make you understood.
The issue is the politics and action of what we do in response to climate change and this means more politics and ethics – not necessarily more science. Or, at least, we cannot continue the naive and dangerous strategy of relying on science alone to somehow do the heavy lifting of what is essentially a political struggle; a hearts and minds struggle between reactionary and progressive visions of the future.
That's why one of the better reactions to Monday's report was from US Secretary of State Kerry: "Let's make our political system wake up and let's make the world respond."
When it comes to climate change scepticism, it's the politics, stupid. The latest IPCC report is a call to ignore those voices urging inaction, or fiddling while the planet burns.
John Barry is Professor of Green Political Economy at Queen's University Belfast