Scientific Errors With the IPCC Statement for Policymakers
The 2007 IPCC Statement for Policymakers (SPM) was released in early Febuary with extensive media attention. However, what has not been discussed are the errors and selective use of data in the presentation of this Report. Policymakers are being mislead in terms of the actual scientific community understanding of climate science. Examples of the errors in the IPCC SPM are discussed in this column.
Several Science Errors (Or, At Best Cherrypicking) In the 2007 IPCC Statement For Policymakers and reads
In even an overview of the section in the 2007 IPCC Statement For Policymakers on “Direct Observations of Recent Climate Change” there are errors, or at best selective information, in their findings. I am summarizing four on this weblog:
1. The IPCC SPM writes on page 7
“… snow cover have declined on average in both hemispheres.”
The Rutgers University Global Snow Lab Northern Hemisphere Snow Cover Anomalies plot through January 2007, however, shows that the areal coverage in the Northern Hemisphere has actually slightly increased since the later 1980s!
Since the inference from the IPCC SPM is that global warming is the reason for these changes, this is at best a clear example of selecting a time period that conforms to their conclusion rather than presenting an up-to-date description of snow cover trends.
2. The IPCC SPM writes on page 7
“Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system.”
It is correct that the ocean is where most of the heat changes occur, but the finding conveniently neglected to report on the significant loss of heat in the period from 2003 to at least 2005;
Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean, Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033.
As stated in that paper,
“The decrease represents a substantial loss of heat over a 2-year period, amounting to about one fifth of the long-term upper-ocean heat gain between 1955 and 2003 reported by Levitus et al. .”
In addition, even with the earlier ocean warming, this is what was found in the paper
Willis, J. K., D. Roemmich, and B. Cornuelle (2004), Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales, J. Geophys. Res., 109, C12036, doi:10.1029/2003JC002260.
” Maps of yearly heat content anomaly show patterns of warming commensurate with ENSO variability in the tropics, but also show that a large part of the trend in global, oceanic heat content is caused by regional warming at midlatitudes in the Southern Hemisphere. ”
They report that,
“……a strong, fairly linear warming trend is visible in the Southern Hemisphere, centered on 40°S. This region accounts for a large portion of the warming in the global average.”
“……..the warming around 40°S appears to be much steadier over the course of the time series, as seen in Figure 7. In addition, this warming extends deeper and is more uniform over the water column than the signal in the tropics. ”
Thus the actual global ocean warming reported in the IPCC SPM over the last several decades occured in just a relatively limited portion of the oceans and through depth such that the heat was not as readily avaiable to the atmosphere as it would be if the warming was more spatially uniform.
Moreover, if the ocean has been absorbing “more than 80% of the heat added to the climate system”, why does the SPM use the surface air temperature trends to define what is a warm year? The IPCC SPM makes such a claim on page 5, where it is written that
“Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850).”
If the ocean absorbs most of the heat (which Climate Science agrees with), than that is the climate metric that should be reported on with respect to global warming, rather than the global average surface temperature trend data.
3. The IPCC SPM writes on page 7,
“The average atmospheric water vapour content has increased since at least the 1980s over land and ocean as well as in the upper troposphere. The increase is broadly consistent with the extra water vapour that warmer air can hold.”
This conclusion conflicts with the finding in
Smith, T. M., X. Yin, and A. Gruber (2006), Variations in annual global precipitation (1979–2004), based on the Global Precipitation Climatology Project 2.5° analysis, Geophys. Res. Lett., 33, L06705, doi:10.1029/2005GL025393,
where they write for the period 1979–2004 that precipitation tends
“have spatial variations with both positive and negative values, with a global-average near zero.”
The global average precipitation has not changed significantly in the period.
If greater amounts of water vapor were present in the atmosphere, the evaporation/transpiration of water vapor into the atmosphere and thus the precipitation would have to increase when averaged globally and over a long enough time period.
4. The IPCC SPM writes,
“Mid-latitude westerly winds have strengthened in both hemispheres since the 1960s.”
This is perhaps the most astonishing claim made in the report. First, peer reviewed papers that have investigated this subject,
Pielke, R.A. Sr., T.N. Chase, T.G.F. Kittel, J. Knaff, and J. Eastman, 2001: Analysis of 200 mbar zonal wind for the period 1958-1997. J. Geophys. Res., 106, D21, 27287-27290.
did find a
“….tendency for the 200 mbar winds to become somewhat stronger at higher latitudes since 1958.”
However, what this means from basic meteorology, is that if the mid-latitude westerlies increase, this indicates a greater north-south tropospheric temperature gradient! This is why the westerlies are stronger in the winter; the troposphere becomes very cold at the higher latitudes, but the tropospheric temperatures change little in the tropics. Thus a statement that the westerlies have become stronger, in the absence of significant warming in the tropical latitudes, indicates a colder troposphere at higher latitude on average.
There is, therefore, an inconsistency in the IPCC SPM. It cannot both be the case that the troposphere in the arctic is warming high while the westerlies in the midlatitudes are increasing in speed. There is a fundamental inconsistency in these trends, which goes unaddressed by the IPCC.
These four examples illustrate the apparent selection of papers and data to promote a particular conclusion on climate change. The science community, and even more importantly, the policy community is ill-served by such cherry picking.
A second weblog is entitled
An Error In The 2007 IPCC Statement For Policymakers On The 2005 Global-Average Radiative Forcing and reads
The 2007 IPCC Statement for Policymakers has a significant error that I have yet to see discussed.
The SPM reports on a “Total Net Anthropogenic” global average radiative forcing for 2005 of +1.6 [0.6 to 2.4] Watts per meter squared. When one converts the units, this means that the Earth’s climate system should be accumulating Joules at a rate of 2.61*10**22 Joules per year [0.98*10**22 Joules to 3.91*10*22 Joules per year] in 2005.
The data, however, show quite a different accumulation of Joules in recent years, and in 2005 in particular. We have often argued that the ocean data has been shown to be an effective way to diagnose the radiative imbalance (see and see). Jim Hansen, for example, has used the accumulation of heat in the upper oceans in the 1990s to bolster his claim of multi-decadal global climate prediction skill (see), where Jim Hansen wrote,
“The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.”
He further writes with respect to the radiative forcing record,
“As the record lengthens, the energy imbalance will provide an invaluable metric defining the task that humanity faces if it wishes to stabilize global climate.”
Well the radiative forcing data record is now longer, and it presents quite a different perspective than a more-or-less monotonic increase in the global radiative forcings as claimed by Jim Hansen. As shown in
Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean,
Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033.
“We observe a net loss of 3.2 (±1.1) × 10**22 J of heat from the upper ocean between 2003 and 2005. Using a broad array of in situ ocean measurements, we present annual estimates of global upper-ocean heat content anomaly from 1993 through 2005. Including the recent downturn, the average warming rate for the entire 13-year period is 0.33 ± 0.23 W/m2 (of the Earth’s total surface area)….”
See their Figure 1 where the accumulation and loss of heat as measured in Joules for the period 1993 to mid-2005 is shown.
This loss of heat from the upper oceans is also consistent with little if any heating in the troposphere over the last several years (e.g. see the last several years in Figure 7 where the trends in the global average tropospheric and stratospheric temperatures are essentially zero). Even if the heat has been transported deeper into the ocean than the about 700m depth analyzed by Lyman et al, the radiative forcing that is available to alter the global average surface temperature trend is much less than reported in the 2007 IPCC SPM, and, indeed, for at least the period from 2003 to 2005 is a negative forcing! Thus, the data indicate a very different picture than presented by the IPCC.
The global average surface temperature trend in the 2007 SPM (see Figure SPM-3 top in the IPCC SPM) continues to show warming, but as has been summarized in
Pielke Sr., R.A., C. Davey, D. Niyogi, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, J. Steinweg-Woods, R. Boyles, S. Fall, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res. in press,
there is a significant warm bias in the construction of a global average surface temperature trend.
What these observations mean is that the statement in the IPCC SPM that there is a positive radiative forcing of 1.6 [0.6 to 2.4] Watts per meter squared in 2005 (when this was not true based on real data) is a particularly egregious error. Rather than relying solely on model based estimates to calculate a global radiative forcing, the authors of the IPCC Report should have also used real world data for the assessment of the net radiative forcing.
A claim that a time period of several years is too short to assess the radiative heating is spurious as long as the sampling of the ocean heat content is sufficiently dense. As discussed in
Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335,
“A snapshot at any time documents the accumulated heat content and its change since the last assessment. Unlike temperature, at some specific level of the ocean, land, or the atmosphere, in which there is a time lag in its response to radiative forcing, there are no time lags associated with heat changes.”
The IPCC finding that the total 2005 net anthropogenic radiative forcing has a best estimate of +1.6 Watts per meter squared and that the total 2005 net radiative forcing has a best estimate of +1.72 Watts per meter squared is inconsistent with the observed changes in upper ocean heat content. The omission of a discussion of the conflict between real world observations and the model estimates of radiative forcing is a serious error in the IPCC SPM.