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Winter Storms in the Northern Hemisphere (1958-1999)
Reference
Gulev, S.K., Zolina, O. and Grigoriev, S.  2001.  Extratropical cyclone variability in the Northern Hemisphere winter from the NCEP/NCAR reanalysis data.  Climate Dynamics 17: 795-809.

What was done
A winter (January-March) climatology of cyclones (storms) was developed and statistically analyzed for the Northern Hemisphere using sea level pressure from NCEP/NCAR reanalysis data for the period 1958-1999.  Only those cyclones that reached a sea level pressure of 1000 mb or lower were utilized in the study.

What was learned
The mean number of cyclones over the Northern Hemisphere winter was 234, although there was pronounced interannual and spatial variability in the record.  Linear trend estimates reveal a statistically significant (95% level) annual decline of 1.2 cyclones per year, suggesting there are now 50 fewer cyclones in the Northern Hemisphere winter than there were 42 years ago.  Additional data analyses suggest that Northern Hemisphere winter cyclones are intensifying at quicker rates and are reaching greater maximum depths (lower sea level pressure) at the end of the record than they were at the beginning of the record.  However, the wintertime cyclones are also experiencing shorter life cycles, dissipating more quickly at the end of the record than in the beginning.

What it means
Winter storms in North America at the end of the 20th century appear to be maturing faster, but dissipating quicker, than they were four decades earlier.  Could this change be the result of global warming?  According to the authors, the phenomenon is probably connected to large-scale features of atmospheric variability, such as the North Atlantic Oscillation and the North Pacific Oscillation.  As for the large decrease reported in the annual number of Northern Hemisphere cyclones over the 42-year period, we note that this observation is in direct opposition to climate alarmist predictions, which suggest the frequency of such events will increase as a result of global warming.  Once again, the predictions of the climate models appear to diametrically opposed to the testimony of nature.