Marcus Yam via Getty Images This is no time to take the high moral ground.

The world has always had droughts, wild storms and all sorts of weather-related natural disasters. There's also a very real phenomenon in the world right now called human-caused climate change. So what, if anything, is the link between climate change and Hurricane Harvey? Broadly speaking, there are three ways you might look at that. The first way is to dismiss the link entirely in provocative terms -- as the conservative pundit Ann Coulter did this week.

I don't believe Hurricane Harvey is God's punishment for Houston electing a lesbian mayor. But that is more credible than "climate change." https://t.co/K7d7mopY5Q — Ann Coulter (@AnnCoulter) 29 de agosto de 2017

Another -- arguably no more helpful -- response is to blame climate change for all weather-related disasters around the world, without direct supporting evidence. The third way? It's not quite as as sexy as the other two. It doesn't give you a simple three-second news grab that says "yeah, climate change is responsible" or "don't be silly, no it's not". But it's the sensible middle ground which essentially argues that a warming climate creates conditions which make severe weather events much more likely. Climate scientist Michael Mann, best known for his so-called "hockey stick" graph which first definitively showed the link between northern hemisphere warming and CO2 emissions, made the link really clear in a Facebook post this week. Wrote Mann: "What can we say about the role of climate change in the unprecedented disaster that is unfolding in Houston with Hurricane Harvey? There are certain climate change-related factors that we can, with great confidence, say worsened the flooding." Mann went on to detail those factors. They included warmer-than-normal air temperatures, and warmer sea temperatures at both the surface and deeper levels. These made the atmosphere in the region of the storm much more moist than usual. Throw in weaker prevailing winds (again, caused by a shift in weather patterns thought to be climate change-related), and you had yourself a great big, almost-stalled storm which was like a massive airborne super-saturated sponge. All that water had to go somewhere -- and go somewhere it did, in the form of unprecedented heavy rain.

LA Times via Getty Images Harvey left a trailer destruction in Houston.

As Mann concluded: "In conclusion, while we cannot say climate change 'caused' hurricane Harvey (that is an ill-posed question), we can say that it exacerbate several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey." Here in Australia, the Climate Council came out firing. "The fingerprints of climate change are all over Harvey," it said. "This is a window into our future. If we don't rapidly reduce our pollution levels now, we can expect worsening extreme weather events." The Climate Council illustrated the phenomenon of warmer sea temperatures leading to increased rainfall in this diagram in its 2016 report Cranking Up The Intensity: Climate Change And Extreme Weather Events.

Climate Council