Hot Today, Cold Tomorrow

As we mentioned in last issue’s Earth Track (Vol. 3, No. 14, p. 8), the global satellite temperature for the month of February was the largest positive anomaly on record—that is, it was the warmest month relative to the long-term (1982–1979) average temperature the satellites had ever measured (Figure 1).

Figure 1. Global satellite-measured temperatures showed that February 1998 was, relative to the mean, the warmest month on record.

Much of the warming was found in the eastern portions of the tropical Pacific, although warmer than normal temperatures stretched around the globe in the tropics. Also, several large regions of much above normal temperatures were found in the Northern Hemisphere mid- and high latitudes—eastern North America, Europe, and central Asia were especially warm.

This pattern has El Niņo written all over it.

We pondered last fall and early winter why the satellite observations were not showing the warm temperatures in the eastern Pacific that surface measurements from ships and buoys indicated, and which were the signals that a big El Niņo was brewing (and subsequently kicked off all of the hype).

Well, now they do.

This lag should actually not have come as a surprise. In fact, in a recent paper, satellite guru John Christy and colleagues defended the satellite data against an attack in which sea surface temperatures (and atmospheric temperatures that were modeled from them) were used to show that the satellite temperatures were incorrectly behaving over the oceans and were therefore too cold. Christy countered by showing that the satellite measurements there matched up nearly perfectly with balloon measurements taken in the same locations. He concluded that the satellite data were indeed correct, and that the relationship between sea surface temperatures and low-to mid–atmospheric temperatures was not simple and direct. The last six months have been a concrete demonstration of this conclusion.

In any event, don’t let the warm temperatures get you down. For lurking just several tens of meters below the surface of the Pacific Ocean are waters whose temperatures are a whopping 6°C colder than normal for this time of the year. This frigid water is making its way upwards, and when it finally reaches the surface, it will have a large cooling effect on global temperatures for months to come. And, undoubtedly, we will kick off a new round of hysteria centering on El Niņo’s evil sister—La Niņa.

References:

Christy, J.R., et al., 1997, How accurate are the satellite ‘thermometers’? Nature, 389, 342–343.