Hi Tom,
Much though I am critical of Hadley Centre projections, see "calling to
account" in [1], it is because they are too optimistic. If their models
suggest that the Amazon rainforest could become a major drought zone,
the models will no doubt be overoptimistic about the time scale. What I
have heard is that, if there are two or three years in a row of drought,
there will be a massive die-off of trees, and the danger of a firestorm
destroying a major part of the forest. If that is true, then we have a
planetary emergency which, like that caused by disappearing Arctic sea
ice, will not be acknowledged by the climate change community.
Similarly the only possible action to get us out of this dreadful
situation is through geoengineering. But the climate change community
and environmentalists continue to wring their hands while saying that
geoengineering is premature.
Why is it that humans require a major disaster before action is taken?
Isn't that going to be the obituary of the human race? "They had the
technology, but didn't have the guts to use it."
John
[1]
http://www.publications.parliament.uk/pa/cm201213/cmselect/cmenvaud/writev/171/arc31.htm
--
On 13/07/2012 16:05, Barker, Tom wrote:
> The Amazon will be a major drought zone if the Hadley projections are correct. They show that the forest has had it unfortunately. Tom
>
> ________________________________________
> From: Discussion list for the Crisis Forum [[log in to unmask]] on behalf of Byron Smith [[log in to unmask]]
> Sent: 13 July 2012 15:52
> To: [log in to unmask]
> Subject: Re: Tropical forests spreading?
>
> Greetings all,
>
> If I may return to the Nature paper by Higgins& Scheiter [1] that Prof Northcott posted a couple of days ago, having now had a chance to read it, I note the following in the penultimate main paragraph:
>
> "Although these projections of increasing tree dominance seem to contradict studies that project forest dieback in the Amazon, this may simply be because our analysis assumes that rainfall remains constant, whereas projections of Amazon forest dieback are based on climate simulations that project decreased rainfall. The high uncertainty in precipitation change over Africa led us to assume that rainfall remained at ambient levels (see Supplementary Information), but future studies should consider changes in rainfall as well as feedbacks between vegetation and rainfall."
>
> So while CO2 trumps temperature in shifting ecosystems from C4 to C3 dominated flora (i.e. savanna/grasslands to forest), hydrological changes could well trump them both, as is generally thought to be most likely for much of Amazonia. Rhett Butler (Mongabay.com), a leading environmental journalists, sought feedback on the paper from a number of Amazon experts concerning the applicability of extending this analysis to South America and found strong reservations across the board.[2] The hydrological projections for Africa that I've seen are indeed mixed, but more recent ones seem to point to some significantly lower levels of precipitation for southern Africa in particular.[3]
>
> And both the opening and final paragraph of the Higgins& Scheiter piece note that land use changes are a further wildcard.
>
> So, yes, acknowledging the complexity of global change trajectories involves honesty about possible negative feedbacks slowing rates of change, as well as appreciating the resilience and adaptability of both natural and human systems. And invoking apocalyptic language and imagery in the discussion of ecological crises confuses both the relevant science and (I would argue) theology. On all this I agree with Michael. But this particular study has some fairly major caveats to observe before it might give us too much hope of a soft landing.
>
> We're not out of the woods (or rather, back into them) yet.
>
> [1] http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11238.html
> [2] http://news.mongabay.com/2012/0712-telegraph-poor-science-journalism.html
> [3] For example: http://journals.ametsoc.org/doi/pdf/10.1175/2009JCLI2317.1.
>
> Regards,
> Byron Smith
>
> PhD candidate
> University of Edinburgh
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