Hottest year on record?

“Usually it’s some time close to the end of a year – say, October or November – before anyone ranks a year in relation to the warmest on record. The British Meteorological Office simply couldn’t wait and on July 31, 2002, rolled the dice that the global temperature during the next five months won’t prove them wrong. Although all they had to go on in releasing their statement was the fact that the first six months of 2002 appear to be the second-warmest on record, without further justification they asserted 2002 "may even break the record [for warmest year] set in 1998." With the following background information, you calculate the odds and decide where to throw your money down.

The temperature anomaly for the warmest year on record (as contained in the Met Office’s own global temperature history since 1856) is 0.593°C. That record was set in the El Niño-dominated year, 1998. 1998 also holds the record for greatest temperature anomaly during its first six months – 0.657°C.

As we’ve already noted and the Met Office has claimed, the first six months of 2002 are the second warmest on record with an anomaly of 0.570°C. This means the anomaly over the remaining six months will have to average 0.617°C for 2002 to break the 1998 record.

Figure 1 shows what’s happened so far this year. The temperature anomaly for each month is represented by the blue bars. The average monthly anomaly required during the next six months in order to break the record is represented by the white bars. Notice how the monthly temperature anomaly has lessened from month-to-month as the year has progressed (red arrow). A considerable string of warm months will be required to break the 1998 record. The trend of the first six months must reverse during the next six for 2002 to become the recordholder.




Figure 1. Temperature anomaly for the first six months of 2002 (blue). White blocks represent the average anomaly necessary in each of the remaining six months in order for 2002 to break the record for warmest year, set in 1998.

Bear with us now. Figure 2 includes data from the thirty-six years in which the first six months were recorded to be warmer than average. It shows the difference in temperature when the average temperature anomaly of the first six months is subtracted from the average temperature anomaly in the second half of the year. We’ve ranked the differences from lowest to highest.

When the blue bars in Figure 2 are negative (below the zero line), this means the second half of the year had a smaller temperature anomaly than the first half. When the bars are on the positive side of the line (above zero), the second half of the year had a greater temperature anomaly than experienced in the first months. In order for 2002 to break 1998’s record, July through December must average 0.046°C above the anomaly experienced from January through June.

What Figure 2 is intended to graphically illustrate is that out of the thirty-six recorded occasions when the first half of the year were warmer than average, only seven times did the temperature anomaly of the years’ second half exceed 0.046°C. This works out to a chance of 19.4%. On that basis (based upon past observation), it seems unlikely that 2002 can edge out 1998.




Figure 2. The temperature difference when the anomaly from the first half of the year is subtracted from the anomaly of the second half of the year, during each year when the first half of the year was warmer than normal. A difference of 0.047°C is needed for 2002 to become the warmest year on record. That’s happened only in seven of thirty-six occasions.

The one thing that might help the Met Office’s boosterism of 2002 as a record breaker would be the development of a strong El Niño, something akin to the one that caused record warmth in 1998. While there is a preliminary indication that an El Niño already has formed in the tropical Pacific, it is characterized as "weak" because most lines of evidence suggest the event will be much less dramatic than that experienced in 1997–98. The U.S. Climate Prediction Center (an organization that closely monitors El Niño activity) said in its July 11, 2002 El Niño Discussion:

The oceanic and atmospheric variables discussed above reflect the presence of El Niño conditions. Most coupled model and statistical model forecasts indicate that El Niño conditions are likely to continue through the end of 2002 and into early 2003. Although there is considerable uncertainty in the forecasts about the timing and intensity of the peak of this warm episode, all of the forecasts indicate that it will be much weaker than the 1997-98 El Niño. It is important to add that the global impacts of this warm episode should be correspondingly weaker than those observed during the very strong 1997-98 El Niño.

Hmmm. This does not bode well for 2002’s Met Office-induced aspirations. (You can access the current U.S. Climate Prediction Center discussion online at http://www.cpc.noaa.gov/products/analysis_monitoring/enso_advisory/.)

Why would the British Meteorological Office shinny so far out on a limb as frail as this? One reason might be that it’s press release resulted in the Reuter’s worldwide news service headline, "World Heads For Warmest Year Yet." Who can calculate the value of that kind of earned media coverage as the world’s environmental ministers convene in Johannesburg, South Africa to celebrate the tenth anniversary of the Framework Convention on Climate Change (Rio Treaty)? We can. The cost is scientific credibility.”

“I didn't read all that 'cause who cares anyway, but here in Maine it's hotter than ever lovin' hell and we've had about one winter worth having in a bunch of years.

I'm movin' to Canada! And when I get there I'm only gonna speak French!”

“where would you go about finding an article as hard to follow as that?”