The Intergovernmental Panel on Climate Change (IPCC) is in the process of preparing its next major report (called AR5 for short) to be published next year. The IPCC has been a strong proponent of human-cause global warming via our carbon dioxide emissions from burning fossil fuels. The IPCC has always downplayed solar forcing saying that total solar irradiance (TSI) is too weak to make much of a difference. In that respect, they have a point. However, the IPCC has always ignored the other, stronger major solar variation, that of the sun’s changing magnetic field which controls the amount of cloud-forming galactic cosmic rays (GCR) reaching our atmosphere.

I reported last year on the CERN experiment which reconfirmed that cosmic rays have a strong influence on cloud formation and hence on climate. In the newly leaked draft report, the IPCC now admits to the “existence of an amplifying mechanism such as the hypothesized GCR-cloud link.”

You can read the whole story about the leaks and their implications at Anthony Watts’ “Watts Up With That”(WUWT) blog here.

The IPCC authors “are admitting strong evidence (“many empirical relationships”) for enhanced solar forcing (forcing beyond total solar irradiance, or TSI), even if they don’t know what the mechanism is.” This directly undercuts the case for anthropogenic global warming.

Refer to WUWT for updates on this breaking story.

Global warming is a funny thing. Whenever we experience a heat wave the press proclaims it is the face of global warming, but when we have an unusual cold snap, it is merely natural variation.

The Arizona Daily Star had an interesting article today concerning the number of days in Tucson with maximum temperatures over 100° F. The story says the record was set in 1994 with 99 days over 100° F and speculates upon our chances of breaking that record this year. The “normal” number of days over 100° F is 62 according to the National Weather Service.

Also interesting is the statistic that July 4, 2012, had the coolest maximum temperature on record, 86°F.

Looking at a larger picture and a slightly different statistic, we see that the greatest number of maximum temperature records in the U.S. were set in the 1930s. Below is a graph compiled by Steven Goddard from U.S. Historical Climatology Network (USHCN) records:

Getting back to Tucson, we see from the graphics in the Star article that we have had more years, with more days over 100° F than “normal” within the last 25 years or so. That could be a reflection of the urban heat island effect. Our asphalt and concrete absorbs more heat and reflects it back at night. I discuss that in my post Warmer nights no proof of global warming.

A graphic from that post demonstrates the problem by comparing the temperature trend in urban Tucson with that from rural Tombstone:

You can see that Tucson temperatures have been rising but there is no trend in the rural Tombstone station. Carbon dioxide works in mysterious ways.

So, the big news from the Arizona Daily Star is: Summers in Tucson are hot.

See also:

Human induced warming in Tucson

Two new investigations found instrument errors in both Arctic and Antarctic temperature measurements that introduced a warming bias into the data. In the Antarctic, the errors produced a warming bias of as much as 18º F.

Antarctic paper:

Atmospheric temperature measurements biases on the Antarctic plateau, published in the Journal of Atmospheric and Oceanic Technology

The abstract reads:

Observations of atmospheric temperature made on the Antarctic plateau with thermistors housed in naturally (wind) ventilated radiation shields are shown to be significantly warm biased by solar radiation. High incoming solar flux and high surface albedo result in radiation biases in Gill (multiplate) styled shields that can occasionally exceed 10°C in summer in case of low wind speed. Although stronger and more frequent when incoming solar radiation is high, biases exceeding 8°C are found even when solar is less than 200 Wm 2. Comparing with sonic thermometers, which are not affected by radiation but which are too complex to be routinely used for mean temperature monitoring, commercially available aspirated shields are shown to efficiently protect thermistor measurements from solar radiation biases. Most of the available in situ reports of atmospheric temperature on the Antarctic plateau are from automatic weather stations that use passive shields and are thus likely warm biased in the summer. In spite of low power consumption, deploying aspirated shields at remote locations in such a difficult environment may be a challenge. Bias correction formulae are not easily derived and are obviously shield dependent. On the other hand, because of a strong dependence of bias to wind speed, filtering out temperature reports for wind speed less than a given threshold (about 4–6 ms 1 for the shields tested here) may be an efficient way to quality control the data, albeit at the cost of significant data loss and records biased towards high wind speed cases.

Arctic paper:

Screen, James A., Ian Simmonds, 2011: Erroneous Arctic Temperature Trends in the ERA-40 Reanalysis: A Closer Look. J. Climate, 24, 2620–2627. doi: 10.1175/2010JCLI4054.1.

The abstract reads:

Atmospheric reanalyses can be useful tools for examining climate variability and change; however, they must be used cautiously because of time-varying biases that can induce artificial trends. This study explicitly documents a discontinuity in the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) that leads to significantly exaggerated warming in the Arctic mid- to lower troposphere, and demonstrates that the continuing use of ERA-40 to study Arctic temperature trends is problematic. The discontinuity occurs in 1997 in response to refined processing of satellite radiances prior to their assimilation into the reanalysis model. It is clearly apparent in comparisons of ERA-40 output against satellite-derived air temperatures, in situ observations, and alternative reanalyses. Decadal or multidecadal Arctic temperature trends calculated over periods that include 1997 are highly inaccurate, particularly below 600 hPa. It is shown that ERA-40 is poorly suited to studying Arctic temperature trends and their vertical profile, and conclusions based upon them must be viewed with extreme caution. Consequently, its future use for this purpose is discouraged. In the context of the wider scientific debate on the suitability of reanalyses for trend analyses, the results show that a series of alternative reanalyses are in broad-scale agreement with observations. Thus, the authors encourage their discerning use instead of ERA-40 for examining Arctic climate change while also reaffirming the importance of verifying reanalyses with observations whenever possible.

Another new paper shows that there are also problems with readings of surface temperatures in the U.S. Historical Climatology Network:

Fall, S., A. Watts, J. Nielsen-Gammon, E. Jones, D. Niyogi, J. Christy, and R.A. Pielke Sr., 2011: Analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends. J. Geophys. Res., 116, D14120, doi:10.1029/2010JD015146.Copyright (2011) American Geophysical Union.

(Full paper here.)

That paper found that poorly-sited stations produced a warming bias whereas well-sited stations showed no century-scale trend.

Criteria for evaluating station siting are given in the table below:

The study found that only 1.2% of stations were in the highest category and 70% of the stations had a warming bias of at least 3.6º F or more. Keep that in mind the next time headlines blare that it was the warmest month, year, decade since…. it was cooler.

See also:

Your Carbon Footprint doesn’t Matter

The State of our Surface Temperature Records

Natural Climate Cycles

Arctic Temperatures: Not So Hot

2010 the 9000th Warmest Year