Ozone depletion, the melting of polar ice caps, melting of Himalayan glaciers – these are observed facts and have been blamed upon the 'Green House Effect and resulting global warming'. The instruments used for monitoring these phenomena are today, satellite borne sensors. The EnviSat, Terra and QuikScat findings reported last week should raise an alarm. The speeding up of glaciers melting, resulting in the formation of glacial lakes in the Himalayas and the melting of snow in Antarctica may be precursors to a global event similar in magnitude to the one, the now extinct Dinosaurs experienced – the only difference being that they perished due to the ice age.

The data available in the archives like the Goddard Institute of Space Studies (GISS), the Global Historical Climatology Network (GHCN) and the United States Historical Climatology Network (USHCN) for mean annual temperature, collected from hundreds of ground based monitoring stations, cannot be used to categorically say that the global mean annual temperatures are on the rise everywhere. To state a few cases – the cities of Stuttgart , Milan, Paris, Albany and many others show a drop. New Delhi shows a perceptible drop in the last six years – which coincides with the strict implementation of CNG usage in most public transport vehicles. The mismatch between space based observations (done in the last twenty years or so) and data from earth bound monitoring stations is a puzzle for our environmentalists to dwell on.

On the technology front – the 'Multiple-Wavelength LiDAR' system for Vegetation mapping designed by the NASA-GSFC has been put to use by the Woods Hole Research Centre to study habitat heterogeneity by characterising vegetation in 3D. This LiDAR uses two lasers with imaging wavelengths of approximately 665nm and 775nm. By calculating the ratio between the returned laser backscatter in these two wavelengths, the differentiation between vegetated and non-vegetated surfaces can be done and also the height of the canopy or vegetated surface be obtained. If wishes were horses... well we should have hyperspectral LiDAR scanners.