AGW to reach…”The Edge of Wetness”… Super-hip Anthony Watts references the Johnny Carson Show to attempt a put down a press release about a paper (An Adaptability Limit to Climate Change Due to Heat Stress) that suggests the following:
Despite the uncertainty in future climate change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation.
Maximum wet-bulb temperatures from a climate scenario with mean temperature 12°C warmer than 2007. Land areas >~34°C exceed the wet-bulb limit of potentially lethal heat stress. (Purdue University/Matthew Huber)
Here’s Anthony’s snappy comeback in its entirety: “Apparently it’s not just the heat, but the humidity too.” Now that’s what I call critical thinking. How is considering the possible impact of a particular level of warming a bad thing?
Wott's Up With That? 
The abstract makes it very clear that these conditions are well beyond those of the heat waves mentioned by the commenters:
Presumably a Tw of at least 35°C need last for only six hours to kill all the mammals in the area. And, presumably this could happen just in a small area.
Whatever the large scale meteorological realities of such high temperature/high humidity conditions, I think it would be much harder to argue against the possibility on a smaller scale, such as in Saudi Arabia. And this possibility would be sufficient to end willful habitation in the general area.
Also see SkepticalScience (11May,2010)
http://www.skepticalscience.com/Heat-stress-setting-an-upper-limit-on-what-we-can-adapt-to.html