Sunday, January 3, 2010

global warming controversies

Canto: Before we go on to look at the causes of modern global warming, how can it be that some aren't convinced that global warming is actually happening? Some are even saying that the globe is cooling.
Jacinta: Well you know that, at least since the Eocene, and probably overall since the beginning of the planet, earth has been cooling, with many fluctuations such as this one. Claims about cooling since 1998 are dealt with here, and on many other sites. The 1998 spike was likely due to a strong El Nino effect, and the 2005 year was also quite warm, but a couple of years of relative coolness since then doesn't buck the overall trend. It's a matter of being patient with data - a year or two's figures aren't enough to reveal an underlying trend.
Canto: And didn't they just release figures for - 2008 was it? Which suggested it was the warmest year on record?
Jacinta: No, 2008 is down at only around equal eighth place, according to the USA's National Oceanic and Atmospheric Administration, and from what I can gather 2009 was warmer, but the decade was the warmest on record - that is, for a mere 150 years or so.
Canto: And even a million years is a mere blip in planetary time.
Jacinta: But we won't get complacent. We want realism, not complacency. This is possibly the fastest upward spike in planetary history, and it may already be out of control.
Canto: So what proof is there that this warming trend is due to human activity?
Jacinta: Here's where we move into difficult waters because of the complexity of the subject. I'm not a scientist, and so I have to defer to the scientists, especially the climatologists of the IPCC who have reached a general consensus on the issue. The February 2007 summary of the IPCC's fourth assessment report stated that there was a ninety percent likelihood that the global warming being experienced was anthropogenic and primarily related to the burning of fossil fuels. This, along with land clearing and other agricultural practices, has increased the level of carbon dioxide and methane in the atmosphere.
Canto: Yet there's a vociferous crowd who argue that this a natural cycle, and that our contribution to the greenhouse gases in the atmosphere is negligible, and even if there is some warming there's no need for all the alarmism. And many of these guys, such as Edward Townes and Joanne Nova and Australia's endless Andrew Bolt, are very tenacious indeed.
Jacinta: And so were the flat-earthers, remember. It's evidence that counts, not tenacity.
Canto: So let's look at the evidence. Joanne Nova presents, on her blog [actually it's guest post by a Dr David Evans], 'a simple proof that global warming is not man-made'. Evans presents graphs and data showing that the vast bulk of emissions occurred after the second world war, with post-war reconstruction and industrialism. In fact, he claims that half of all human emissions [presumably throughout human history] occurred from the seventies on. However, he claims, global warming began after the 'little ice age', approximately from 1700, and has been trending up ever since. He argues that, if it was all to do with anthropogenic emissions, this would be better represented in the figures, with little or no warming before 1945. So what do you say to that?
Jacinta: Next time.

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