Global Warming Science -


Amazon Drought


[last update: 2010/07/06]



The Amazon: A Severe drought in 2005 caused low river levels. The most recent study indicates the Amazon is not nearly as vulnerable to drought as the alarmists claim. At the end of this document: a look at the effect on atmospheric CO2.




2010 Recent Study


A new study published in 2010 in the Geophysical Research Letters, as reported in Science Daily:




From the above article:


·         "We found no big differences in the greenness level of these forests between drought and non-drought years, which suggests that these forests may be more tolerant of droughts than we previously thought," said Arindam Samanta, the study's lead author from Boston University.


·         The IPCC is under scrutiny for various data inaccuracies, including its claim -- based on a flawed World Wildlife Fund study -- that up to 40% of the Amazonian forests could react drastically and be replaced by savannas from even a slight reduction in rainfall.



A previous NASA study provides the following figure with the caption “During the 2005 drought in the Amazon, intact primary forest showed an increase in photosynthetic activity (left image) despite below-average rainfall (right image). Data from NASA's Terra satellite (left) showed areas of higher (green) and lower (red) growth during the peak of the drought (July-Sept.). Data from the Tropical Rainfall Measuring Mission satellite (right) showed areas of severe rainfall reduction due to the drought (red) and few areas with above normal rainfall (blue).” []



The above NASA study states: “Global climate models predict the Amazon forest will cut back photosynthesis quickly when a drought starts. ... By contrast, the research team's findings suggest the opposite happens, at least in the short-term. The drought-induced flush of forest growth would dampen global warming, not accelerate it.




Contradictory Studies












Defying Dry: Amazon Greener in Dry Season Than Wet





Amazon Drought 2005


A study of the causes and impacts of the drought (Zeng et al, 2007) states:

precipitation over the Amazon is thought to be largely controlled by the El Ni˜no Southern Oscillation (ENSO) originating in the equatorial Pacific Ocean. However, the equatorial Pacific was largely neutral during 2005. If anything, there were cold SST anomalies in the eastern Pacific toward the end of the year normally associated with a wetter Amazon. … 2005 had relatively small rainfall change, compared to, e.g., the large 1997–98 drought, seemingly inconsistent with the extremely low river and lake levels seen by people living in the region. Part of the answer to the latter question comes from the observation that the major El Ni˜no events such as 1997–98 and 1982–83 that led to large negative rainfall anomalies in the Amazon were short lived (about 1 year), and often immediately followed by La Ni˜na events that led to anomalously wet conditions which allowed land to recover quickly from the dryness. In contrast, although the 2005 rainfall anomaly was not particularly large, it was preceded by another dry period of 2002–03 (an El Ni˜no year), with little recovery in 2004, which had lingering central Pacific warm conditions. Thus precipitation stayed below normal for 4 years from 2002 to the end of 2005.



The following figures are from the above study.





The above paper studied the correlation between the Amazon rainfall and the Southern Oscillation Index (SOI and North Atlantic sea surface temperatures (NATL SST). “The correlations with SOI and NATL are significant at 95% level over large area of the Amazon basin.” The following figure is from the study. In the late 1980s-early 1990s there was an extended El Nino period (negative SOI), but this was counteracted by lower N. Atlantic SST (green box in figure below). In the early 2000s the El Nino and N. Atlantic SST were in sync causing extended reduced rainfall (orange box in figure below).




The following figure from the above Zeng et al study, shows the Amazon precipitation for the 10 datasets plus Obidos streamflow and Tabatinga river stage data.




The following figures are from the study by Aragao et al “The extent and impacts of the 2005 drought”, which states: “Causes of the 2005 Amazonian drought: Reduction of Trade Winds from the north > Northwards displacement of the ITCZ > Rainfall decrease over Amazonia








Amazon CO2 Factory


Reuters: “Amazon's 2005 drought created huge CO2 emissions” states the “2005 drought in the Amazon rainforest killed trees and released more greenhouse gas than the annual emissions of Europe and Japan, an international study showed … The experts estimated that the forest had been absorbing 2 billion tons of carbon dioxide a year on average since the 1980s but lost 3 billion in the 2005 drought, which killed trees and slowed growth. The total impact was an extra 5 billion tons of carbon dioxide in the atmosphere. That is more than the annual emissions of Europe and Japan combined.” []


What was the impact of the extra 5 billion tons of CO2 (more than the annual emissions of Europe and Japan combined) on global atmospheric CO2?


The following figures show CO2 at a couple of the NOAA measuring stations (graphs from The only CO2 monitoring station in South America started in 2006. Thus the nearest stations (Easter Island, Chile and Ragged Point, Barbados are shown).






No noticeable impact. Apparently Europe and Japan could cease all emissions and accomplish nothing.