Coincidentally, following on from my review of the first part of the Woods Hole letter yesterday, Bishop Hill follows the scent, looking at the underlying evidence cited in support of the IPCC claim of 40 percent of the Amazon forest being at risk from a slight reduction in rainfall.
This impacts directly on the second part of the letter, which I was planning to review today and forms the substance of this post. It is there, in that second part, that we see William Y Brown, president and CEO of the Woods Hole Research Center (WHRC), assert that:
Mr Booker's criticism of the IPCC's claim that 40 percent of the Amazonian forest is threatened by global warming, on the grounds that it was based on a WWF claim, misses the fact that the WWF's statement was supported by several peer-reviewed science articles, including four published by the WHRC.Bishop Hill does a tolerable job of tracking down some of this "support", but the point that would elude most readers is the very close connections between the WWF and WHRC. They share a common agenda and work closely together. Daniel Nepstad, the "senior scientist" on the staff of WHRC specialising in the Amazon, has worked for WWF. Some of his studies, notably this one, were part-funded by the WWF.
This highlights the difficulty anyone has in following the various claims and counter-claims on this issue. Many of the papers produced purport to be scientific explorations but they are in fact disguised advocacy directed at pursing a wholly political agenda.
That applies to WHRC and especially Daniel Nepstad. Nothing he writes or is associated with can be taken at face value. To ignore the political dimension is to afford advocacy the same status as genuine science. Nepstad is an advocate, using the guise of science to make his case, his medium the "peer reviewed" paper, giving his work entirely spurious authority.
Part of the strategy is to place such papers and then use them as a basis for self-citation and campaigning, locking in the arguments without reference to the wider issues and other views. By keeping focused on the very narrow issues, the agenda is thus set.
The classic example is precisely the paper linked immediately above, which is entitled: "Interactions among Amazon land use, forests and climate: prospects for a near-term forest tipping point". The lead author is Nepstad. Appearing in Philosophical Transactions of the Royal Society in May 2008, it offers this dire prediction:
If sea surface temperature anomalies (such as El Nino episodes) and associated Amazon droughts of the last decade continue into the future, approximately 55 percent of the forests of the Amazon will be cleared, logged, damaged by drought or burned over the next 20 years ...This is one of the papers published post-IPCC which supposedly supports the IPCC claim (which also originated from Nepstad), so we thus have a situation where the WHRC is citing Nepstad of the WHRC ... supporting Nepstad.
Even on its own merits, the paper (or this statement) can be dismissed. Firstly, it offers outrageous non-sequiturs - linking clearance and logging with "sea surface temperature anomalies". All three are entirely independent variables. Either clearance or logging could account for substantial loss of the forest, entirely unrelated to temperatures.
Secondly, the prediction relies on the presumption that "sea surface temperature anomalies (such as El Nino episodes) and associated Amazon droughts of the last decade continue into the future". Yet there is no observational evidence that either will continue into the future. Since the once-in-a-hundred-years drought of 2005, there has been – as we have reported elsewhere - above-average rainfall in large parts of the Amazon basin.
This is where it gets really interesting, and we have to follow several parallel themes to get to the bottom of Brown's assertion. Firstly, one of the papers on which Brown apparently relies is one to which Nepstad himself draws attention in arguing that the IPCC statement is "correct".
This is published in 1994 in Nature, where the authors (including Nepstad) estimate that half of the closed forests of Brazilian Amazonia depend on deep root systems to maintain green canopies during the dry season. The finding is based on work in northeastern Pará, itself a northeastern state of Brazil, outside the equatorial zone where there is a defined dry season.
Therein lies a singular problem. It is by no means clear how that helps in supporting a claim that slight reductions in rainfall could flip 40 percent of the entire Amazonian forest into savannah (especially when the Brazilian forest is less than half of the total area). But that is the measure of dealing with Nepstad. He sprays out citations like a tomcat marking his territory, but trying to pin down exact numbers in them is like trying to bottle smoke.
At the heart of it all though - as we see from Huntingford et al (2003) - the likes of Nepstad rely on Cox et al. (2000, 2001). They are using a Hadley Centre "coupled climate model" for their predictions.
The Huntingford paper, currently, is particularly relied upon by Simon Lewis, who is complaining against Jonathon Leake's rendition of "Amazongate", claiming that the IPCC statement was "scientifically defensible and correct".
What neither Nepstad nor Lewis admit to though is the fallibility of their model. That models generally are fallible is startlingly demonstrated by Oyama and Nobre (2003), who ran different versions of an atmospheric general circulation model. In one, they found no change from the current situation. In other, savannahs replaced eastern Amazonian forests and a semi-desert area appeared in the driest portion of Northeast Brazil.
Thus, the results are entirely dependent on the input, something admirably illustrated by Merengo 2006, who draws attention to the major uncertainties in modelling Amazonian climate, and the substantial errors and divergences in datasets.
Any serious student of the situation, however, should be aware that some of the uncertainly was resolved in a paper published by Malhi et al on 13 February 2009 (online) in the Proceedings of the National Academy of Science. Entitled, "Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest", this revisited the models on which Nepstad and Lewis rely, finding that "most tend to underestimate current rainfall."
Taking into account the differences between model-simulated and observed rainfall regimes in the 20th century, the authors concluded that dry-season water stress was likely to increase in eastern Amazonia over the 21st century. But, they found, the region still "tends toward a climate more appropriate to seasonal forest than to savannah."
Eastern Amazonia is one of the more vulnerable areas, where there is a defined dry season – as opposed to the equatorial areas where rainfall is more or less constant throughout the year, and it is there that problems will be particularly acute. The finding directly contradicts the second Oyama and Nobre model and the Nepstad/Lewis Armageddon scenario. It definitely contradicts the IPCC's 40 percent claim. If eastern Amazonia survives, so does most of the rest of the forest.
Despite that, Lewis - in his complaint to the Press Complaints Commission – still asserts that: "It is very well known that in Amazonia tropical forests exist when there is more than about 1.5 meters of rain a year, below that the system tends to 'flip' to savanna (sic), so reductions in rainfall towards this threshold could lead to rapid shifts in vegetation."
This, though, is not based on observation but on the very climate modelling that Malhi et al have essentially discredited. Amongst other findings, they suggest that there are no sharp vegetation thresholds in areas of different rainfall.
Some savannah is found in predominantly forest climates, and some evergreen forests are found in dry climates. Other factors, such as local surface hydrology and soil properties, e.g., seasonal flooding, can favour savannah in dry forest climates. Shallow water tables can allow gallery or riverine forest to persist in dry savannah climates, or more fertile soil may favour trees over grasses.
Crucially, what makes an important difference is the length of the dry season and the amount of water retained on the soil and, if this falls below a broad transition zone, there is "a gradual shift in the relative abundance of savannah relative to forest."
Furthermore, and of vital importance to the whole argument, they see evidence of what they call "demographic inertia" - inertia caused by long lifespans and slow community turnover. In the forest system, they assert, this may delay any forest dieback.
Moreover, they say, the presence of forest may modify local microclimate (evapotranspiration, rainfall generation, exclusion of invading grasses, shading of soil surface, and seedlings) sufficiently to favour the persistence of forest ("microclimatic inertia"). Once established, closed-canopy, deep-rooted forest may persist even if the local climate has shifted to savannah conditions
In other words, here is a reasoned argument which suggests that any transition, far from being rapid, may be gradual and in many cases will not happen at all.
This though, is only one strand of the wider argument. Alongside Nepstad's paper which appeared in Philosophical Transactions of the Royal Society in May 2008 (cited earlier), were 26 others in an edition dedicated to the Amazon. One was a paper by Mayle and Power which explored the "Impact of a drier Early–Mid-Holocene climate upon Amazonian forests".
Their paper used a palaeoecological approach to examine the impact of drier climatic conditions of the Early–Mid-Holocene (ca 8000–4000 years ago) upon Amazonia's forests and their fire regimes. During the Early–Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal (i.e., transitional) areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semideciduous dry forests.
Elsewhere in the Amazon basin, though, they found "considerable spatial and temporal variation in patterns of vegetation disturbance and fire," which probably reflected "the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests - and Palaeo-Indian land use."
Their analysis thus showed that the forest biome in most parts of Amazonia appeared to have been "remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning." Only in ecotonal areas was there evidence of biome replacement in the Holocene. From this palaeoecological perspective, therefore, Mayle and Power argued against the Amazon forest "dieback" scenario simulated for the future.
So far, then, we have two papers – variously suggesting only gradual and limited dieback, greater forest resilience and encroachment of savannah in transitional areas. But there is more.
Lewis makes great play of the claim that the: "most extreme die-back model predicted that a new type of drought should begin to impact Amazonia". He asserts that, in 2005, it happened for the first time: "a drought associated with Atlantic, not Pacific sea-surface temperatures." And it is this 2005 drought which underpins many of the alarmist claims.
Needless to say, Lewis is wrong. This was not the first time, by any means, the Amazon had experienced such a drought. This is evident from a paper by Marengo (2009) which looks at: "Long-term trends and cycles in the hydrometeorology of the Amazon basin since the late 1920". It reports (relying on an earlier paper by the same author) that the drought of 1963–1964, like the drought of 2005, occurred during non El Nino years.
In a fascinating paper, Marengo offers detailed evidence of significant climate variability in the Amazon basin, of differences in rainfall patterns between north and south, and of a "succession of relatively wet and dry periods (cycles) of approximately 20–30 years, suggesting indicators of long-term variability on multi-decadal time scales."
Furthermore, the cyclical variations are different, north and south, and climatic changes affect the two regions in different ways – while one area can get drier, the other can become wetter (which is exactly what happened in the 2005 drought, ruling out any idea that conditions observed in any one area can be used to predict what might happen across the entire basin).
Marengo offers several papers on this "cyclical variation" theme, one from 2006 where he refers to inter-annual variability and also to the paucity of data. But in this and his later paper, reference is made to decadal changes in climate being "more due to natural climate variability". And particularly damning for the Nepstad/Lewis axis is this observation:
From a statistical analysis of the hydrometeorological series, it is concluded that no systematic unidirectional long-term trends towards drier or wetter conditions have been identified since the 1920s. The rainfall and river series showing variability at inter-annual scales linked to El Niño Southern Oscillation was detected in rainfall in the northern Amazon. It has a low-frequency variability with a peak at - 30 years identified in both rainfall and river series in the Amazon. The presence of cycles rather than a trend is characteristic of rainfall in the Amazon.Similar observations are found in Zeng et al (2006) and Coe et al (2002), all leading inexorably to the conclusion that Nepstad and his fellow climate activists are over-interpreting short-term phenomena, superimposing a trend when longer-term data suggest climate variability.
Thus, addressing William Y Brown and his assertion that there is support for the IPPC claim, not only does that seem not to exist – as Bishop Hill adequately demonstrates – the protestations of support (Brown included) come from a very limited band of activists who cross-refer to each other. Outside that clique, the wider scientific community suggests a different and variable picture, one which is largely at odds with that suggested by climate activists.
As it stands, therefore, the IPCC statement is an orphan – entirely unsupported. Brown is throwing up a smokescreen which, like his assertion that Woods Hole Research Institute is a "scientific institution", is thoroughly dishonest.
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