Sunday, January 14, 2007

Was 2006 really the warmest year on record for the U.S.?

An article in The New York Times by Andrew Revkin entitled "Agency Affirms Human Influence on Climate" tells us that "2006 was the warmest year for the 48 contiguous states since regular temperature records began in 1895. It surpassed the previous champion, 1998", but is that really true? The so-called warming trend is cited as evidence of Global Warming and Climate Change due to the effects of man-made greenhouse gases, notably carbon dioxide. The article is based on an annual report from the National Oceanic and Atmospheric Administration (NOAA) entitled "Climate of 2006 - Annual Report", specifically the sub-report entitled "2006 Annual Climate Review- U.S. Summary", and described in a news release entitled "NOAA REPORTS 2006 WARMEST YEAR ON RECORD FOR U.S. - General Warming Trend, El Niño Contribute to Milder Winter Temps" which opens by stating that "The 2006 average annual temperature for the contiguous U.S. was the warmest on record and nearly identical to the record set in 1998." That seems clear enough, but there is more to the story.

It turns out that analysis of the data is not as cut and dry and final as some commentators lead you to believe. The NOAA news release states that:

NOAA originally estimated in mid-December that the 2006 annual average temperature for the contiguous United States would likely be 2 degrees F (1.1 degrees C) above the 20th Century mean, which would have made 2006 the third warmest year on record, slightly cooler than 1998 and 1934, according to preliminary data. Further analysis of annual temperatures and an unusually warm December caused the change in records.

So, the data is still in a state of flux. Further, if you look at the 1934, 1998, and 2006 data points, you see that they are very close and don't "obviously" lead one to conclude an absolute trend.

Furthermore, the report goes on to say that additional revisions to this data are likely:

An improved data set being developed at NCDC and scheduled for release in 2007 incorporates recent scientific advances that better address uncertainties in the instrumental record. Small changes in annual average temperatures will affect individual rankings. Although undergoing final testing and development, this new data set also shows 2006 and 1998 to be the two warmest years on record for the contiguous U.S., but with 2006 slightly cooler than 1998.

So, yes, right now 2006 is considered the record year for the U.S., but not by much and 1998 is expected to reclaim the record not too many months from now. Either way, neither year, nor any of the past 25 years has been that much warmer than 1934.

Furthermore, this is only for the continental U.S. The Global Summary section of the NOAA report states that:

The global annual temperature for combined land and ocean surfaces in 2006 was +0.54°C (+0.97°F) above average, ranking 5th warmest in the period of record. However, uncertainties in the global calculations due largely to gaps in data coverage make 2006 statistically indistinguishable from 2005 and several other recent warm years as shown by the error bars on the global time series. Globally averaged land temperatures were +0.78°C (+1.40°F) and ocean temperatures +0.45°C (+0.81°F) above average, ranking 4th and 5th warmest, respectively. The land and ocean surface temperatures for the Northern and Southern Hemisphere ranked 2nd and 6th warmest, respectively.

Or to summarize: On a global scale, 2006 was not a record year for temperature and in fact ranked only 5th.

For the Northern Hemisphere, 2006 was in fact the 2nd warmest year, but for the Southern Hemisphere it was the 6th warmest year.

For the record, NOAA is the agency of record for climate data. Also for the record, I personally have a lot of confidence in NOAA, provided that they stick to their knitting and give us hard data and hard science and refrain from engaging in speculation and forecasting of the distant future or concerning government policies.

The main point of the Times article was the extent to which NOAA is now claiming or admitting that "a buildup of greenhouse gases was helping warm the climate." The Times quotes the news release as saying that "A contributing factor to the unusually warm temperatures throughout 2006 also is the long-term warming trend, which has been linked to increases in greenhouse gases." The full paragraph from the news release is:

The unusually warm start to this winter reflected the rarity of Arctic outbreaks across the country as an El Niño episode continued in the equatorial Pacific. A contributing factor to the unusually warm temperatures throughout 2006 also is the long-term warming trend, which has been linked to increases in greenhouse gases. This has made warmer-than-average conditions more common in the U.S. and other parts of the world. It is unclear how much of the recent anomalous warmth was due to greenhouse-gas-induced warming and how much was due to the El Niño-related circulation pattern. It is known that El Niño is playing a major role in this winter's short-term warm period.

The Times was careful to caveat its quote by characterizing the news release as "emphasizing that the relative contributions of El Niño and the human influence were not known." To be very clear, the news release stated:

It is unclear how much of the recent anomalous warmth was due to greenhouse-gas-induced warming and how much was due to the El Niño-related circulation pattern. It is known that El Niño is playing a major role in this winter's short-term warm period.

In other words, the debate over global warming, at least at the hard-data science level is still open and certainly not "over" as many "Climate Change" commentators continue to claim.

I'm all in favor of doing more and better research on climate, but will resist efforts to prematurely rush to dramatic conclusions that are not very clearly justified by hard-data real science.

NOAA struggles mightily to do short-term weather and climate predictions, and they really are the premier agency when it comes to climate knowledge and expertise. The idea that climate can be forecast decades into the future is a dubious concept at best.

The NOAA news release states:

U.S. and global annual temperatures are now approximately 1.0 degrees F warmer than at the start of the 20th century, and the rate of warming has accelerated over the past 30 years, increasing globally since the mid-1970s at a rate approximately three times faster than the century-scale trend. The past nine years have all been among the 25 warmest years on record for the contiguous U.S., a streak which is unprecedented in the historical record.

That sounds rather horrendous, but we do need to be careful not to read too much into that reading of the data. Or any specific reading, for that matter. In fact, it turns out that half of the top 10 temperature years for the U.S. were more than fifty years ago:

  1. 2006
  2. 1998
  3. 1934
  4. 1999
  5. 1921
  6. 1931
  7. 1990
  8. 2001
  9. 1953
  10. 1954

Notice that the four consecutive years 2002, 2003, 2004, and 2005 don't even make the top 10. Only four of the past ten years made the top 10.

It is worth noting that "the historical record" used by NOAA goes back only to 1895. That seems to me to be far too short a base period to use to forecast climate decades into the future. Sure, scientists (and pundits) can make their best guess based on that limited data and use sophisticated models, but guesses are still guesses and models are not implicitly hard forecasts of the future, and as we say in computer science, "garbage in, garbage out."

The technical term for man-made greenhouse gases is anthropogenic greenhouse gases. It turns out that water vapor is in fact categorized as a greenhouse gas and is the primary greenhouse gas, ahead of carbon dioxide. For reference, here is what NOAA has to say about the greenhouse effect:

The greenhouse effect is unquestionably real and helps to regulate the temperature of our planet. It is essential for life on Earth and is one of Earth's natural processes. It is the result of heat absorption by certain gases in the atmosphere (called greenhouse gases because they effectively 'trap' heat in the lower atmosphere) and re-radiation downward of some of that heat. Water vapor is the most abundant greenhouse gas, followed by carbon dioxide and other trace gases. Without a natural greenhouse effect, the temperature of the Earth would be about zero degrees F (-18°C) instead of its present 57°F (14°C). So, the concern is not with the fact that we have a greenhouse effect, but whether human activities are leading to an enhancement of the greenhouse effect.

Will 2007 be a warmer year? Hard to say. I know that it was fairly warm back east, but it has been colder here in the northwest. Personally, I'd like to see another decade of data before getting too excited that the past 25 years is indicative of the trend for the next 25 years.

-- Jack Krupansky

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