Senator Ted Cruz, chairman of the Senate Space, Science, and Competitiveness subcommittee, held a public hearing Dec. 8, 2015, “Data or Dogma?: Promoting open inquiry in the debate over the magnitude of human impact on Earth’s climate,” coinciding with the Paris Climate Conference.
Cruz invited to testify at his hearing three global warming contrarian scientists, an author, and one scientist supporting the 97 percent scientific consensus that Earth is warming and we are the cause. A balanced “open inquiry” might have had 97 scientists for the scientific consensus against the three contrarians, minus the author, but this was Cruz’s hearing.
In his introductory remarks Cruz introduced his three main arguments for the hearing:
“According to the satellite data there has been no significant global warming over the last 18 years”;
“The satellite data are the best data we have”;
and “Public policy should follow the actual science and the actual data and evidence and not political and partisan claims …”
This denier myth has been shown to be false. Cruz presented a graph showing 1998, the warmest year recorded at that time, followed by 18 years of little or no warming. But he failed to mention NOAA and NASA jointly released their global temperature data, making it official: 2015 was the hottest year on record (since 1880). In fact, the top 10 hottest years have all happened since 1998, and six have been hotter than 1998. These include in order of increasing temperature 2009, 2005, 2013, 2010, 2014, and 2015. And so far 2016 has set monthly temperature records for January and February.
Here we get into the discussion of the best source of global temperature data: surface thermometers or satellites. A paranoid but popular denier myth is that climate scientists are adjusting the surface thermometer data from thousands of automated weather stations and ocean buoys in a global conspiracy to make it look as though Earth is warming.
Actually, raw data from both surface thermometers and satellites are regularly adjusted for valid scientific reasons. What Cruz did not say is the satellite data are adjusted even more than the thermometer data, and the satellite data are considered by most scientists as less reliable.
Surface thermometers measure temperature directly and the raw data are adjusted for different ocean collection methods (buckets vs buoys), instrument calibration, instrument surface coverage (particularly low in the Arctic, which is warming fastest), changes in instruments, changes in site conditions, etc.
Satellites do not measure temperature directly, they are not “thermometers in the sky.” Instead satellites measure microwave radiation from atmospheric oxygen molecules which is converted to temperature using complex model assumptions, which are prone to error. As satellites look down from space their altitude resolution is not very good (What altitude is being measured, 30,000 feet or 50,000 feet?). Clouds and precipitation significantly reduce satellite temperature measurements in the low to mid troposphere, and satellites do not measure the same location above the surface at the same time every day, as thermometers do.
Adjustments are made for orbital drift (changes in location above Earth) and decay (loss of altitude due to atmospheric friction), calibration of new and old satellites using different instrumentation, changes in solar radiation, etc. And, satellites do not measure the surface, where we live, they measure the troposphere, up to 11 miles above our heads.
I don’t think any scientist would argue against basing U.S. climate policy on the very best climate science. Unfortunately, Cruz says data should guide public policy, then ignores the data and unquestioningly embraces the denier dogma.
So what data are the best? An article in The Guardian, “Ted Cruz fact check: which temperature data are the best?” (1/18/2016), suggests surface temperatures are best because: they are five times more reliable than satellite data; many different groups processing the raw surface thermometer data arrive at more consistent final temperature estimates; oceans trap over 90 percent of the Earth’s warming while the troposphere retains only two percent; and the surface is where people live.
In a response to the “Data or Dogma?” hearing, Ben Santer, of the Lawrence Livermore National Laboratory, and Carl Mears, Remote Sensing Systems, wrote: “Climate policy should be formulated on the basis of both the best-available scientific information and the best-possible analysis and interpretation. Sadly, neither was on display at the Senate hearing…. There was no attempt to provide an accurate assessment of uncertainties in satellite data…. Political Theater trumped true ‘open inquiry’. Climate change is a serious issue, demanding serious attention from our elected representatives in Washington. The American public deserves no less.”
Why is all this important? If you ignore the data, as Cruz does, and create doubt, then you can ignore the problem.
William Gran, now retired, was an adjunct instructor at Greenfield Community College on global warming and climate change. He can be reached at whgran@gmail.com