'little ice age' is a complex and controversial event, with the IPCC describing it as a series of more or less connected regional effects rather than a 'globally synchronous increased glaciation'. And since there's just no agreement on the timing and duration of this soi-disant little ice age, it's almost impossible to come to a determination of causes. Possibilities include the usual suspects - low solar radiation, volcanism, natural climate variability, ocean current activity - and some new human factors, which I'm none too convinced about. The fact is, though, that the reasons for the warming between the end of the little ice age, whenever that was, and around 1950, remain unclear. What is quite clear to the vast majority of climatologists is that the warming since 1950 has been largely due to human fossil fuel burning and land clearing.
Canto: From my cursory reading, I gather that Dr Barry Brook is of the view that human effect on greenhouse gas levels and global warming, previous to 1950, and even 1850, has been considerably underestimated. But what I also notice from this cursory reading is how head-spinningly complex this multi-factorial issue actually is. Endless difficulties in measurement, in interpretation, in extrapolation and prediction. It's hardly surprising that nonscientific but naturally sceptical types like myself can be so thoroughly discombobulated, what with radiative forcings, radiosonde data, solar-cycle lengths, carbon sink capacities, tropical hotspots, biomes, urban heat islands, and more and more.
Jacinta: A pleasant puddle of dummy spit there, Canto, but I think it's best if we keep our eye on the big picture, while gradually trying to educate ourselves on these undoubtedly significant details. And the big picture is that there is an apparently accelerating rise in global temperatures, the effects of which are currently being felt especially in the northern hemisphere. The large-scale burning of fossil fuels and the continuing clearing of forest areas that act as carbon sinks, and various other large-scale human practices, seem to be having an effect upon the climate. Certainly this is the consensus view of the experts in the field, and though there may be assessment flaws here and there, and exaggerations on the fringes, we would surely be unwise not to act on this general consensus.
Canto: But what will be the effects of this global warming, and what should we do about it? I mean, given that the Eocene warming led first to extinctions then to speciations, what with the hot and steamy atmosphere just right for reproduction, the future surely doesn't look all bad? Maybe there'll be a collapse of the human population, and after a period the warming will level out, and the cooling trend will start again. That's a reasonable scenario isn't it? And all of this will have a transformative impact on the biosphere, like many previous transformative impacts.
Jacinta: Yes but I think the area of really unfamiliar territory is the speed of this temperature rise. If it continues like this for, say, a century, it might well be more catastrophic than anything that has gone before. I agree though that some species will thrive. Mass extinctions may not have a negative impact on the whole biomass, but it's generally top of the food chain species that are most vulnerable, paradoxically.
Canto: You mean us? I'm not sure if we're talking out of our arses, but it's kind of exciting stuff. I wonder if we somehow require doom and gloom scenarios to get us motivated.