Global Warming Science -


Costa Rica


[last update: 2010/03/03]





The following two figures are from the IPCC AR4, 2007. The left figure shows warming of 0.05-0.1 degrees C per decade from 1901 – 2005.  The right figure compares the temperature anomalies with the climate models (blue band including only natural climate forcings, pink band including anthropogenic CO2) for Central America. According to the IPCC models, CO2 started to have an effect in the 1970s. The models also fail to reproduce the warming in the 1940s.









Costa Rica has 4 temperature stations in the NOAA GHCN database, only 3 of which have data after 1980. No data are earlier than 1950 for these 3 stations. The following figure shows the 3 temperature stations in the GHCN database indicated with red arrows. At the top of the figure, the Hadley Climatic Research Unit (HadCRU) data for the 5x5 degree grid is shown, indicated with the green arrow. All three GHCN stations are within this grid. (HadCRU provides the data used by the IPCC).






The following figure shows the HadCRU (CRUTEM3) grid temperature anomaly for the 10-15N, 80-85W grid (as shown above) superimposed on the IPCC models plot. Costa Rica doesn’t exhibit as much recent warming as Central America, and no long-term warming is evident.





The following figure shows the temperature of Puntarenas – monthly temperature data are shown in blue and the annual average temperature in red (temperatures from the NOAA GHCN database). No warming trend is evident.




The following figure shows the annual total precipitation for Puntarenas (blue) and Juna Santcosta (red) (precipitation from the NOAA GHCN database). No trend is evident.






The Golden Toad


The lack of a local “global warming” trend doesn’t stop the blame game. The BBC reported (based on an article in Nature magazine) that climate change was causing the demise of Costa Rica’s golden toads, which live in the Monteverde Cloud Forest.




The BBC article [] stated: “Clouds in the mountains of Costa Rica now form at higher altitudes than they did previously, so the frequency with which the forests are mist-clad has declined.” The New Scientist magazine reported the scientists ”make a convincing case blaming global climate change” []. According to the World Wildlife Fund []: “Its extinction has been attributed to a number of factors including pollution, weather, and climate change due to global warming.” 


Humans may be responsible, but not due to CO2-based global warming – deforestation is a more likely culprit.


According to the Santa Elena Cloud Forest Reserve []: “99.8% of Costa Rica’s 51 000 square kilometers was originally covered with lush tropical forests”; “by 1950 one quarter of the tropical forests were destroyed. During the period from 1950 to 1985, Costa Rica had one of the highest deforestation rates in Central America, during which time a further 50% of forests were destroyed. Currently only approximately 26% of the land remains under forest”; “increased demands for land primarily for agriculture has been the primary cause for deforestation”; “a decade ago over a third of the country’s land surface was severely eroded, and that another third was subjected to increased flooding and subtler forms of erosions”.


A 2001 study published in Science (“Climatic Impact of Tropical Lowland Deforestation on Nearby Montane Cloud Forests” by R. O. Lawton, U. S. Nair, R. A. Pielke Sr, R. M. Welch – authors from Departments of Biological Sciences and Atmospheric Sciences, University of Alabama and Colorado State University,  []) stated: “Tropical montane cloud forests (TMCFs) depend on predictable, frequent, and prolonged immersion in cloud. Clearing upwind lowland forest alters surface energy budgets in ways that influence dry season cloud fields and thus the TMCF environment. Landsat and Geostationary Operational Environmental Satellite imagery show that deforested areas of Costa Rica's Caribbean lowlands remain relatively cloud-free when forested regions have well-developed dry season cumulus cloud fields. Further, regional atmospheric simulations show that cloud base heights are higher over pasture than over tropical forest areas under reasonable dry season conditions. These results suggest that land use in tropical lowlands has serious impacts on ecosystems in adjacent mountains.


The Rainforest Alliance quotes Robert Lawton [[: “croplands and grasslands reflect more of the solar energy that impinges on them than do forested lands. Typically, croplands and grasslands have shallower rooting. Typically, more of the rainfall that hits them runs off as stream flow, so less stays in the local system. The shallower rooting, more runoff, and less water mean that grasslands transpire less -- they evaporate less water. Since they are using less energy in the evaporation of water, they are often physically, tangibly hotter than forested land, and they transfer more energy as this sensible heat by conduction and convection into the atmosphere.


The following figure shows the rampant deforestation visible on Google maps satellite image view. Almost the entire upwind area to the cloud forest has been deforested. This has resulted in less transpiration reducing the humidity for in the cloud forest.





Update: 2010/03/03: Studies Now Blame a Skin Fungus for Demise of Golden Toad


global warming did not kill the Monteverde golden toad, an often cited example of climate-triggered extinction, says a new study.” [] “Many researchers have linked outbreaks of the deadly chytrid fungus to climate change, but the new study asserts that the weather patterns, at Monteverde at least, were not out of the ordinary. The golden toad vanished after an exceptionally dry season following the 1986-1987 El Niño, probably not long after the chytrid fungus was introduced.” The report also notes: “Proving a link between climate change and biodiversity loss is difficult because so many overlapping factors may be at play, including habitat destruction, introduction of disease, pollution and normal weather variability. This is especially true in the tropics, because written weather records may go back only a few decades, preventing researchers from spotting long-term trends.