Global warming caused by the greenhouse effect of rising CO2 may do all sorts of bad things for people. Weather patterns may change, ice sheets melt and the sea may inundate low-lying land. However, before rushing to implement expensive measures of doubtful efficacy, we should remember that there might be beneficial effects as well.

Energy industry sources, such as the Greening Earth Society, have long suggested that one effect will be longer growing seasons, especially in northern latitudes where according to surface temperature measures, most warming has occurred. Environmentalists have generally ridiculed such claims and argued that earlier supportive satellite data up to 1991 covered too short a period to draw firm conclusions.

However a paper last week (Zhou et al 2001) extends the record up to 1999 and clearly shows an lengthened growing season in areas where the warming has been greatest, particularly Siberia. There has not been much change for the United states overall, but we should not be surprised at this, since US surface temperatures have changed little either.

If Zhou and colleagues interpretation is correct, these longer growing seasons would be expected to have increased farm productivity, so that more food is produced on less acres and food prices fall. This is exactly what has happened since 1981, the period of the study. Russian food shortages, a regular feature of the cold 1960s and 70s are now a thing of the past.

It will be interesting to see how the press treats this good news story.

Myneni, R.B., et al., 1997. Increased Plant Growth in the Northern High Latitudes from 1981 to 1991. Nature, 386: 698–702.

Zhou, L., Tucker, C.J., Kaufmann, R.K., Slayback, D., Shabanov, N.V. and Myneni, R.B. 2001. Variations in northern vegetation activity inferred from satellite data of vegetation index during 1981 to 1999, Journal of Geophysical Research, 106(D17): 20069-20083.