|
|---|
INSIDE
|
 |
|
Isotopic techniques have long proved valuable in studying groundwater and improving water resource management. More recently, they have been applied to investigating "global warming" and climate changes.
Spanning more than 6 million km2, the Amazon Basin contains roughly half of the world's tropical forest. This gigantic evaporative basin accommodates roughly 80,000 plant species and possibly 30 million animal species, mostly insects. The Amazon River contributes 20 percent of the world's river discharge into oceans. But accelerating deforestation is seriously threatening this unique ecosystem and, with it, the global environmental balance.
The IAEA has been working to understand this phenomenon for more than a decade. In 1985, the Agency launched a project supporting environmental research in Brazil. The multi-disciplinary, isotope-aided studies of the effects of changing land use on the ecology and climate of the Brazilian Amazon combined the efforts of some 80 scientists from several Brazilian institutes. The Agency supplied laboratory equipment and provided expert missions to co-ordinate and advise local counterparts, 23 of whom were granted training abroad. The initiative received five years funding from Sweden and support from other research organizations outside Brazil. The joint FAO/IAEA Division and the Isotope Hydrology Section of the Agency's Division of Physical and Chemical Sciences provided technical back-up.
Concluding their work in 1993, the Amazon Basin studies validated a regional isotope model of the transport of water, revealing that 50 percent of the Basins precipitation consists of recycled water. This high contribution of recycled water makes the water cycle sensitive to deforestation, which on such a large scale will change the regional water balance through reduction of the evapotranspiration flux to the atmosphere. This causes more water to run off to the rivers and local temperatures to rise. Results from today's climate models suggest, moreover, that a complete and rapid destruction of the Amazon forest would be irreversible, having serious consequences not only for the local but also for the global climate.
The Amazon Basin studies are but one example of the widening scientific concern that large-scale human activities - such as deforestation and energy production - may significantly alter the world's climate in the near future. Global warming due to the steadily increasing concentrations of the so called "greenhouse" gases (GHGs) is one part of that impact. Naturally occurring GHGs, primarily water vapour and carbon dioxide (CO2), are vital in regulating the temperature of the earth and its atmosphere. However, excess emissions - mainly of CO2 from the combustion of fossil fuels, methane (CH4) produced from agricultural production and chlorofluorocarbons (CFCs) synthesized in various industrial processes - could cause temperature and rainfall patterns to shift and natural ecosystems to be destroyed.
So far, it appears that man-induced changes on the climate are fewer than those occuring naturally. Nevertheless, climate change remains a serious long-term concern because any alteration in the radiative balance of the atmosphere will lead to changes in evaporation and precipitation. To understand the complex processes regulating the global ecosystem, an integrated research approach needs to be taken involving analysis of both present and past climate changes. Here again, environmental isotopes are powerful investigative tools.
The IAEA-initiated Global Network for Isotopes in Precipitation (GNIP) became operational in 1961 when a world wide survey of the isotope composition of monthly precipitation began in collaboration with the World Meteorological Organization (WMO). The primary aim was to collect systematic global isotope data (oxygen-18, deuterium and tritium) to characterize the spatial and temporal variability of isotope concentrations in precipitation. The data gathered has been used extensively in hydrological investigations within the scope of water resources inventories, planning and development.
The network started with around 100 meteorological stations collecting data from more than 60 countries and territories. Some years later, the total number of stations in operation reached 220. The network's database has also proved indispensable in palaeoclimatology, and provides important input for verifying and improving atmospheric circulation models.
In support of these global investigations, the Agency has provided training and equipment in isotope applications through 13 technical co-operation projects during the last 10 years at a total budget of $28.1 million. Over 100 scientists from developing member states have been trained in related disciplines through workshops and training courses during the period. Support continues to be provided through coordinated research programmes (CRPs) that support national environmental investigations. For instance, Argentina is participating in a CRP to reconstruct paleoclimatic and palaeoenvironmental conditions during the last glacial cycle (20,000 years ago), in cooperation with 13 other countries. Argentina's lead scientist on the project is Dr. Hector Osvaldo Panarello of the National Atomic Energy Commission, who participated in Agency training courses in Latin America during 1991 and 1993. Initial results from the project are quite significant as they reveal a temperature difference between Holocene and the Last Glacial Maximum of about 5 degree Celsius. These results have important implications for the modeling of global climate.
| Contents | HomePage | WorldAtom | TecAtom |