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Amazon drought: the least of their worries

Posted by Richard Sunday, March 14, 2010

A poster child of the warmist creed, the Amazon rainforest is back in the news today, with an article in a Sunday newspaper. It asserts that a new study, funded by NASA, "has found that the most serious drought in the Amazon for more than a century had little impact on the rainforest's vegetation."

This is a reference to the Samanta paper which we reviewed yesterday, on which basis we are told today that the findings appear to disprove claims by the IPCC that up to 40 percent of the Amazon rainforest could react drastically to even a small reduction in rainfall and could see the trees replaced by tropical grassland.

Certainly, the IPCC claim is damaged by Samanta, but the findings cannot be taken to support assertions that the 2005 drought had little impact on the forest. Insofar as he can be relied upon at all, Nepstad demonstrated in a 2008 paper published by The Royal Society that significant damage did occur. This is reinforced by a later paper summarised here.

However, these findings can hardly be unexpected of an exceptional drought. Moreover, it was undoubtedly more damaging than it might otherwise have been as it occurred after a run of below average precipitation, not least in 2003 when the ground water was not fully recharged in large areas of the Amazon basin.

The Samanta paper, therefore, leaves open the wider debate on the fate of the Amazon. But, for reasons which will become apparent by the end of this week, it is becoming more and more important that it should be resolved. There are political issues here which have major ramifications for Western policy and potentially huge economic consequences. Thus, we are revisiting the issue, exploring wider aspects of this ongoing controversy.

If we start by distilling the warmist claims, their argument seems to be that the run of dry weather in the period 2002-2005, culminating in the exceptionally severe drought, is a harbinger, signalling a long-term change in the rainfall pattern as a result of "climate change".

Under the influence of hypothesised higher temperatures, the Met Office Hadley Centre coupled climate-carbon cycle model predicts severe drying in the Amazon region which initiates forest loss. As trees are lost, transpiration reduces, resulting in less rainfall. This "positive feedback", exacerbated by logging, clearance and fires, causes the loss of up to half the forest and its replacement with savannah-like grassland.

What is terribly suspicious about the current debate though is that history seems to stop in 2005, with the great drought. Numerous papers have been written about this event but we are now five years down the line and we hear very little about the intervening years.

One suspects that, if the drought of 2005 had continued – given the media bias favouring Armageddon scenarios – we would have been assailed by reports of deteriorating conditions. On the other hand – and especially with experience of weather conditions close to home – one also suspects that 2005 and the preceding years could have been part of natural climate variability, albeit an extreme example of it.

That latter suspicion is apparently well-founded as a paper published in August 2002 notes that "climatic variability strongly impacts the hydrology of the [Amazon] basin", with "short (∼3–4 years) and long (∼28 years) modes of precipitation variability". Further, a paper published in April 2006 had reported "major flooding" in the 1984-2001 period.

Likely as not, therefore, after a period of drought lasting 3-4 years – Hadley model notwithstanding - one might expect a period of normal or even above-average rainfall. But, needless to say, an exploration of scientific literature on this proved unhelpful. The international media, though, yielded considerable information.

In March 2006, for instance, - the year following the great drought - there were reports of severe flooding in Bolivia, The highlands and most of the rivers of the Amazon basin overflowed affecting 27,500 families, with 12,742 in need of humanitarian aid. Later, floods in Columbia were reported to have killed 32 people and injured 30 others in five provinces.

The following April brought reports of floods caused by "unusually heavy rains in Brazil's Amazon region" which had killed six people and forced tens of thousands more to flee their homes. Officials had declared a state of emergency in 15 municipalities where at least 21,000 people had evacuated to avoid Amazon River tributaries that had breached their banks.

The worst flooding had been in the city of Maraba, 1,250 miles northwest of Rio de Janeiro, where the Tocantins River had risen to 40 feet above its normal level.

With the rainy season over, Friends of the Earth were predicting more drought in the Amazon. The year 2007, however, brought more news of disastrous floods in Amazonian Peru, followed by news of Bolivia battered from the Andes to its Amazon lowlands by "devastating floods".

By mid January 2007, at least 50 people had been killed in southeastern Brazil, due to flooding and landslides brought on by torrential rains. The hardest hit areas had been the coastal state of Rio de Janeiro and mountainous Minas Gerais, north of Rio de Janeiro.

In February, "after weeks of disastrous flooding" in the eastern, tropical lowlands, 69,000 families were affected, roads were cut across the country and 35 people were dead. By the March, Bolivia was suffering its worst floods for 25 years. This, of course, did not stop the BBC reporting: "Amazon 'faces more deadly droughts'".

A month later, Pachauri was in full flow, with the publication of his IPCC report, telling the media that there was "high confidence" that eastern parts of the Amazon will gradually change to savannah from forest. Northern Brazil, by then, was suffering its worst flooding for decades. Heedless of this, by the end of the year, The Washington Post was retailing the views of Daniel Nepstad, author of a new WWF report, at the UN climate change conference in Bali. He was warning of the effects of drought in the Amazon.

Two months later, in February 2008, Peru was reporting that almost half a million people had been affected by rains and extensive flooding of their homes and crops. Bolivians in the city of Trinidad were terrified that floodwater would inundate them, while their president Evo Morales decreed a national disaster. Some 30,890 square miles in the Amazonian province of Beni were under water, an area roughly the size of Austria.

This coincided with news that climate models were increasingly forecasting a dire future for the Amazon rainforest. They were based on research linking drought in the Amazon to sea surface temperatures in the tropical Atlantic. Higher temperatures and less rainfall were predicted. Meanwhile, Brando, Nepstad, et al were warning that multi-year severe drought "can substantially reduce Amazon forest carbon stocks."

In April, though, severe rainstorms were affecting Equador bringing the worst flooding in a decade, killing 47 people and damaging crops and infrastructure. That same month 33 people had died in two weeks of flooding in north-east Brazil. More than 77,000 people had been made homeless, with officials warning that the heavy rain would continue.

Only days later, The Daily Telegraph reported: "Amazon doomed by too much clean air", telling us that the rainforest was coming under threat from attempts to curb the pollution that causes acid rain.

The link was found by a team from the University of Exeter, Centre for Ecology and Hydrology, Met Office Hadley Centre and Brazilian National Institute for Space Studies. The team was estimating that by 2025 a drought on the 2005 scale could happen every other year and by 2060 such a drought could occur in nine out of every ten years. As for when the forests could disappear, "2060 isn't a bad guess," we were told.

By November, reports were coming in that flooding and landslides triggered by heavy rain that had been pounding southern Brazil for nearly two months. They had killed at least 84 people and forced more than 54,000 to flee. The weekend of the 22-23rd had brought as much rain as normally fell over several months.

More than 1.5 million people had been affected by the heavy rains. Eight cities in the state of Santa Catarina remained cut off by water and blocked roads. The region was under a state of emergency. The governor declared that the region faced, "the worst weather tragedy in history." A climatologist from the Brazilian National Institute for Space Research warned that the floods could be "an early consequence of global warming."

In January 2009, the WWF was still worried about the rate of deforestation. In February though, some scientists were suggesting that parts of the Amazon rainforest might face less serious droughts than had been previously feared. They had compared 19 global climate models with actual rainfall measurements for the region. They all tended to underestimate current rainfall levels.

Many citizens of Peru would have agreed. By April 2009, the current rainfall levels had filled the Amazon to its highest level since records began. And, as the rain began to pour in Brazil, May saw people huddled in cow pens converted into emergency shelters as swollen rivers rose, the homeless number rising to over 300,000 and the death toll to 60.

A month later and the floods were being described as the worst for 56 years. In Manaus, a city deep in the jungle, the Negro river rose to 88.32 feet, just short of the 1953 record. Satellite pictures showed the extent of the flooding. Of course, it was "caused by climate change".

There was no let up in the "climate change". The states of Rio de Janeiro and São Paulo suffered torrential downpours through the December and into the New Year. Over 90 people died and more than 1,800 people were without shelter. Nearly 6,000 were displaced. Scores of people were killed by mudslides as well as the floods. Rio de Janeiro's vice governor observed: "People had never seen so much rain in this region."

Then, thousands of tourists were stranded at the historical site of Machu Picchu in Peru after torrential rain had flooded the area, setting off lethal mudslides that killed five people.

So persistent was the rain that, by February, it had made its way to the Huanaco region, burying streets and homes under up to five feet of water. Thousands had to abandon their homes in the city of Tingo Maria. Rising water affected more than 4,000 people, flooding their homes and cars and "sweeping just about everything in its path downstream." The downpour was Peru's heaviest in 15 years.

Of Peru's 25 regions, 17 were facing destruction from the rains that had started in December. By the end of February, the National Civil Defense Institute reported that more than 22,700 people had been left homeless and more than 108,000 had suffered damage to homes, crops or other assets.

This month, Bolivia was back in the news with 40,000 families in the Amazonian eastern provinces completely stranded by floods. The rainy season had been particularly intense and resulted in flooding in this area of Bolivia almost every year since 2005, said the news report.

However, not all of this could be blamed on heavier rain, much less "climate change". As early as 1980, researchers were noting increased runoff due to deforestation. The long-predicted regional climatic and hydrological changes that would be the expected result of Amazonian deforestation may already be beginning, they observed.

Similar observations were being made in 1987. But, it was remarked, one should not exclude the possibility that observed trends might be elucidated without invoking human intervention, even if "major inundations are likely to polarise concerns and dim the memory of moderate floods."

And therein lies some profound wisdom. The most recent weather events do tend to "polarise concerns". In 2005, after two years of depressed rainfall, against the background of "climate change" and models predicting more of the same, drought became the obsession of the climate community, polarising their concerns.

Although there have been localised droughts since, especially in the south, but also in Venezuela and several highland provinces of Ecuador, there has been nothing remotely approaching the scale of the 2005 event. While the climate community remains obsessed with drought, the actuality is of five continuous years of excess rainfall since 2005, effectively returning to the pattern observed during the 1984-2001 period.

A year after the 2005 drought, researchers were writing of their concerns that, while the rainforest had adapted to seasonal and short-term drought, it might be less resilient to longer term climate change. Given current weather patterns, that should be the least of their worries.