Background
The authors indicate that "most multi-cellular terrestrial organisms experience climate at scales of millimeters to meters," yet they say that "most species-climate associations are analyzed at resolutions of kilometers or more," in what is "commonly known as the 'bioclimate approach' or 'climate envelope' modeling." However, they go on to say that "because individuals experience heterogeneous microclimates in the landscape, species sometimes survive where the average background climate appears unsuitable," which phenomenon is something that the vast majority of bioclimate studies do not consider in their analyses.

What was done
In an effort designed to illustrate these facts, Suggitt et al. recorded temperatures in numerous micro-sites at two locations where the vegetation was relatively homogenous (the Lake Vyrnwy Royal Society for the Protection of Birds reserve in Wales, and High Peak in the Peak District National Park in England) in September 2007 and January 2008, as well as in numerous micro-sites within three different habitat types (woodland, heathland and grassland) located within Skipwith Common in North Yorkshire, UK, in September 2008 and January 2009.

What was learned
The seven scientists report that "thermal differences between habitats, and slope and aspects, were of the same order of magnitude as projected increases in global average surface temperatures," and they indicate that in some cases, microclimate variation exceeded estimates of warming under all of the IPCC's emissions scenarios, "which range from 1.1 to a 6.4°C rise in global mean temperatures (IPCC, 2007)."

What it means
Suggitt et al. write that "these large temperature differences provide opportunities for individual organisms that are able to move short distances to escape unfavorable microclimates," and, hence, that "populations may shift microhabitats (slopes, aspects and vegetation density) in response to inter-annual variation in the climate." Thus, they say their results indicate that "the incorporation of habitat and topographical information is essential for species that (a) have some level of flexibility in their habitat associations, and (b) are at least partially limited by temperature extremes," bearing witness to the fact that in the real world of nature, the 'bioclimate approach' or 'climate envelope' modeling are not adequate for describing how different species will respond to future changes in climate, such as the global warming that is predicted by state-of-the-art climate models.

Reference
IPCC. 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom.