Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 14:37 GMT le 17 février 2010
Earth's lower atmosphere recorded its warmest January on record last month, according to data from both the University of Alabama, Hunstville (UAH) and Remote Sensing Systems (Figure 1). The satellite measurements used to take the global temperature of the lower atmosphere began in December 1978, using the Microwave Sounding Unit (MSU) on polar-orbiting satellites. The January 2010 temperature anomaly was an impressive 0.72°C above the 1979 - 1998 average, easily beating the previous record of 0.59°C set in January 2007. Last month's anomaly was the 3rd warmest anomaly for any month, falling just 0.04°C cooler than the record warmest anomalies of 0.76°C from February and April 1998. The January 2010 satellite-measured temperatures continued a trend of very warm conditions we've seen in the lower atmosphere since the current El Niño event began in June 2009. Record high temperatures occurred in November 2009, and were the second highest on record in both July and September 2009, according to UAH. The record-breaking temperatures in the lower atmosphere are due to the heating of the atmosphere by the strong El Niño event that has been heating the waters of the Central and Eastern Pacific since June 2009, combined with the global warming trend of the past few decades. Since we are currently at the lowest level of solar output in decades, the Earth is currently about 0.1°C cooler than if we were near the maximum of the 11-year sunspot cycle. Had we been near solar maximum, we would have set an all-time warmest lower atmosphere temperature anomaly record last month.(Note, though, that there is about a 2-year time lag between solar maximum and when Earth's global temperature responds). It will be interesting to see if the current El Niño event, which is quite a bit weaker than the record-strongest El Niño of 1998, is capable of making 2010 beat 1998 for honors as the warmest year on record in the lower atmosphere.
Figure 1. Temperature of the lowest 8km of the atmosphere measured by satellite via the MSU instrument flown on polar-orbiting satellites between 1979 - 2010. Image credit: Dr. Roy Spencer, University of Alabama, Hunstville.
Real-time display of atmospheric temperatures measured by satellite
The University of Alabama, Huntsville has a handy interactive plotting page that lets one plot up the historical and near-real-time satellite measurements of Earth's global average temperature at various levels of the atmosphere. These temperatures are measured by the MSU instrument on the polar-orbiting NOAA-15 satellite. Note that this is a different instrument than the AQUA satellite's MSU instrument used by UAH to formulate their official monthly global temperature anomaly data set. The two satellites give similar results, although NOAA-15 requires an additional correction to account for drift of the satellite.
Figure 2. Temperature of the global atmosphere at 14,000 feet (4.4 km) as measured by the MSU instrument on the polar-orbiting NOAA-15 satellite. This instrument has been flying since August 1998. The 20-year average (yellow line) and 20-year record highs (pink line) are for the period 1979 - 1998, using versions of the MSU instrument that flew on older satellites. The most recent data (green line), as of February 15, 2010, are marked by a white square, and have now fallen below the record for the date set in 1998. Note that during July 2009, November 2009, and January 2010, record high temperatures were measured at 14,000 feet altitude. A full description of the data is available from the University of Alabama, Hunstville.
Error sources in global atmospheric temperatures measured by satellite
Satellite-measured temperatures of Earth's atmosphere, in my judgment, are inferior to using the surface based system of ground stations and ocean buoys for measuring global temperature changes. I have two reasons for saying this:
1) The satellite temperatures show large global increases when there is an El Niño event. While the surface also experiences an upward spike in temperatures during an El Niño, it is much less pronounced than the atmospheric heating that occurs. Since we live at the surface, those temperatures are more relevant.
2) According to a description of the MSU data available on the Remote Sensing Systems web site where the data is archived,
"The instruments in the MSU series were intended for day to day operational use in weather forecasting and thus are not calibrated to the precision needed for climate studies. A climate quality dataset can be extracted from their measurements only by careful inter-calibration of the eleven distinct MSU instruments."
In other words, it's very tricky to make an accurate measurement of Earth's temperature going back to 1979, when satellite measurements began. You have to merge data from eleven separate satellites, whose instruments were never designed to make the kind of precise long-term climate measurements that are being asked of them. While surface stations also have error sources, I believe that the uncertainty in the satellite-based global temperature measurements are higher.
Dr. John Christy of the University of Alabama, Huntsville, made a series of efforts to perform the careful inter-calibration needed beginning in the 1990s, and for over a decade successfully defended his conclusion that the MSU instruments were showing a much lower level of tropospheric warming than what climate models predicted. Christy was probably the most quoted scientist by the "greenhouse skeptics" during that period, and testified numerous times before Congress about his findings. This discrepancy was a prime argument Senator James Inhofe (R-Oklahoma) used in his famed 2003 speech when he referred to the threat of catastrophic global warming as the "greatest hoax ever perpetrated on the American people." Greenhouse contrarian Dr. S. Fred Singer, who has probably more Congressional testimony about global warming under his belt than any other scientist, headlined his SEPP website for many years with the quote, "Computer models forecast rapidly rising global temperatures, but data from weather satellites and balloon instruments show no warming whatsoever. Nevertheless, these same unreliable computer models underpin the Global Climate Treaty." Michael Crichton also used the tropospheric warming discrepancy to give climate models a bad rap in his State of Fear novel. However, a series of papers published in 2004 and 2005 showed that the satellite inter-calibration methods used by Christy were incorrect. Christy conceded that his analysis had been in error, and participated in writing a statement put out by NOAA's Climate Change Science Program that detailed the error.
Climate change contrarians continue to prefer using the UAH satellite data to look at global temperature trends, since that data set shows less warming than the regular surface station data sets, and rates 1998 as the warmest year on record. The UAH data shows that in the 31-year period from 1979 - 2009, Earth's lower atmospheric temperature warmed by 0.13°C per decade. A separate analysis of the satellite data by Remote Sensing Systems (RSS) puts this number at 0.15°C per decade. For comparison, NASA's GISS and the UK HadCRUT surface data sets (which don't use satellite data) show warming of 0.16°C and 0.15°C per decade, respectively. You can generate these numbers yourself, using the excellent woodfortrees.org plotting tools. The amount of global warming predicted in the 2007 IPCC report for the period 2010 - 2030 was 0.20°C per decade, so we are running about 25% below this predicted level of warming, when averaging over the past 31 years.
For further reading: I have a 2006 blog post on this, and realclimate.org has a technical discussion.
Portlight continues relief efforts in Haiti
The Portlight.org disaster-relief effort continues in Haiti, with another container of specifically-requested medical supplies being shipped today. At the request of Portlight's on-site coordinator, Richard Lumarque, Portlight is committed to sending another container with 500 tents plus food and water. The cost of each shipment is $4300, so your donations are greatly appreciated! Please visit the Portlight.org blog to learn more and to donate. Floodman's blog has the latest info on Portlight's plan for Haitian relief.
Figure 3. Richard Lumarque, Portlight's on-site coordinator in Haiti, poses with double-amputee Darline Exidor, who received a wheelchair from Portlight. Portlight's team of ten relief workers has been laboring full-time the past two weeks to deliver donated supplies and assess the needs of the earthquake survivors.
I'll have a new post on Thursday or Friday.
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