I'm only going to focus on the data at this point.
The IPCC has been invoked, and why not go to the source? The IPCC and Al Gore won a Nobel prize for awareness on global warming, so if anyone wants to invoke their studies I'll be glad to show a link.
Have you read anything beyond the Summary for Policy Makers? Anyway, you should know that the IPCC does not actually study anything, it is a committee that collects studies that supports its stated view that humans cause climate change.
Throughout the report, the IPCC lists a considerable number of uncertainties with respect to its own high confidence. The listing of these uncertainties can be found throughout the AFAR IPCC 2007 (you have to go beyond the SPM), particularly in the chapters dealing with their selection of evidence to support their contention of the primacy of human causes. Some of the uncertainties briefly outlined in the Technical Summary of the AFAR are shown below.
The relative blandness of many of these stated uncertainties here and throughout the IPCC AFAR 2007 can obscure the fact that there is a considerable lack of understanding concerning the climate, and that as a result, scenario projections are actually very poor when employed as a means to predicting the future. Once again, the IPCC indicates a very low level of scientific understanding with respect to natural causes for climate variability. That statement is
absolutely crucial in that global temperature changes over the past 100 years have been dwarfed by earlier historical variations in temperature, and that this noted change in global temperature falls
well within the mean of the past 4,000 years.
Of course the IPCC pays attention to only its own consideration for what constitutes an uncertainty, but they are considerable. Also, the document does not contain either any dissenting reports from its member scientists (and there are critical members of the IPCC); nor does it acknowledge direct criticism concerning its main assumption of change in climate due only - or primarily - to human activity.
IPCC uncertainties concerning changes in human and natural drivers of climate (p.81):
The full range of processes leading to modification of cloud properties by aerosols is not well understood and the magnitudes of associated indirect radiative effects are poorly determined.
The causes of, and radiative forcing due to stratospheric water vapour changes are not well quantified.
The geographical distribution and time evolution of the radiative forcing due to changes in aerosols during the 20th century are not well characterised.
The causes of recent changes in the growth rate of atmospheric CH4 are not well understood.
The roles of different factors increasing tropospheric ozone concentrations since pre-industrial times are not well characterised.
Land surface properties and land-atmosphere interactions that lead to radiative forcing are not well quantified.
Knowledge of the contribution of past solar changes to radiative forcing on the time scale of centuries is not based upon direct measurements and is hence strongly dependent upon physical understanding.
IPCC uncertainties concerning observations of changes in climate in the atmosphere and on the surface (p.82):
Radiosonde records are much less complete spatially than surface records and evidence suggests a number of radiosonde records are unreliable, especially in the tropics. It is likely that all records of tropospheric temperature trends still contain residual errors.
While changes in large-scale atmospheric circulation are apparent, the quality of analyses is best only after 1979, making analysis of, and discrimination between, change and variability difficult.
Surface and satellite observations disagree on total and low-level cloud changes over the ocean.
Multi-decadal changes in DTR are not well understood, in part because of limited observations of changes in cloudiness and aerosols.
Difficulties in the measurement of precipitation remain an area of concern in quantifying trends in global and regional precipitation.
Records of soil moisture and streamflow are often very short, and are available for only a few regions, which impedes complete analyses of changes in droughts.
The availability of observational data restricts the types of extremes that can be analysed. The rarer the event, the more difficult it is to identify long-term changes because there are fewer cases available.
Information on hurricane frequency and intensity is limited prior to the satellite era. There are questions about the interpretation of the satellite record.
There is insufficient evidence to determine whether trends exist in tornadoes, hail, lightning and dust storms at small spatial scales.
IPCC uncertainties concerning snow, ice and frozen ground (p.83):
There is no global compilation of in situ snow data prior to 1960. Well-calibrated snow water equivalent data are not available for the satellite era.
There are insufficient data to draw any conclusions about trends in the thickness of Antarctic sea ice.
Uncertainties in estimates of glacier mass loss arise from limited global inventory data, incomplete area-volume relationships and imbalance in geographic coverage.
Mass balance estimates for ice shelves and ice sheets, especially for Antarctica, are limited by calibration and validation of changes detected by satellite altimetry and gravity measurements.
Limited knowledge of basal processes and of ice shelf dynamics leads to large uncertainties in the understanding of ice flow processes and ice sheet stability.
IPCC uncertainties concerning oceans and sea levels (p. 84):
Limitations in ocean sampling imply that decadal variability in global heat content, salinity and sea level changes can only be evaluated with moderate confidence.
There is low confidence in observations of trends in the MOC.
Global average sea level rise from 1961 to 2003 appears to be larger than can be explained by thermal expansion and land ice melting.
IPCC uncertainties in the paleoclimate record with respect to the IPCC presentation (p.85):
Mechanisms of onset and evolution of past abrupt climate change and associated climate thresholds are not well understood. This limits confidence in the ability of climate models to simulate realistic abrupt change.
The degree to which ice sheets retreated in the past, the rates of such change and the processes involved are not well known.
Knowledge of climate variability over more than the last few hundred years in the SH and tropics is limited by the lack of palaeoclimatic records.
Differing amplitudes and variability observed in available millennial-length NH temperature reconstructions, as well as the relation of these differences to choice of proxy data and statistical calibration methods, still need to be reconciled.
The lack of extensive networks of proxy data for temperature in the last 20 years limits understanding of how such proxies respond to rapid global warming and of the influence of other environmental changes.
IPCC uncertainties in the attributing climate change to human activity (p.86):
Confidence in attributing some climate change phenomena to anthropogenic influences is currently limited by uncertainties in radiative forcing, as well as uncertainties in feedbacks and in observations.
Attribution at scales smaller than continental and over time scales of less than 50 years is limited by larger climate variability on smaller scales, by uncertainties in the small-scale details of external forcing and the response simulated by models, as well as uncertainties in simulation of internal variability on small scales, including in relation to modes of variability.
There is less confidence in understanding of forced changes in precipitation and surface pressure than there is of temperature.
The range of attribution statements is limited by the absence of formal detection and attribution studies, or their very limited number, for some phenomena (e.g., some types of extreme events).
Incomplete global data sets for extremes analysis and model uncertainties still restrict the regions and types of detection studies of extremes that can be performed.
Despite improved understanding, uncertainties in model simulated internal climate variability limit some aspects of attribution studies. For example, there are apparent discrepancies between estimates of ocean heat content variability from models and observations.
Lack of studies quantifying the contributions of anthropogenic forcing to ocean heat content increase or glacier melting together with the open part of the sea level budget for 1961 to 2003 are among the uncertainties in quantifying the anthropogenic contribution to sea level rise.
IPCC uncertainties with respect to their modeling of future climate (p.87):
A proven set of model metrics comparing simulations with observations, that might be used to narrow the range of plausible climate projections, has yet to be developed.
Most models continue to have difficulty controlling climate drift, particularly in the deep ocean. This drift must be accounted for when assessing change in many oceanic variables.
Models differ considerably in their estimates of the strength of different feedbacks in the climate system.
Problems remain in the simulation of some modes of variability, notably the Madden-Julian Oscillation, recurrent atmospheric blocking and extreme precipitation.
Systematic biases have been found in most models’ simulations of the Southern Ocean that are linked to uncertainty in transient climate response.
Climate models remain limited by the spatial resolution that can be achieved with present computer resources, by the need for more extensive ensemble runs and by the need to include some additional processes.
IPCC uncertainties concerning climate equilibrium and transient climate sensitivity (p.88):
Large uncertainties remain about how clouds might respond to global climate change.
A proven set of model metrics comparing simulations with observations, that might be used to narrow the range of plausible climate projections, has yet to be developed.
Most models continue to have difficulty controlling climate drift, particularly in the deep ocean. This drift must be accounted for when assessing change in many oceanic variables.
Models differ considerably in their estimates of the strength of different feedbacks in the climate system.
Problems remain in the simulation of some modes of variability, notably the Madden-Julian Oscillation, recurrent atmospheric blocking and extreme precipitation.
Systematic biases have been found in most models’ simulations of the Southern Ocean that are linked to uncertainty in transient climate response.
Climate models remain limited by the spatial resolution that can be achieved with present computer resources, by the need for more extensive ensemble runs and by the need to include some additional processes.
IPCC uncertainties concerning global projections (p.89):
The likelihood of a large abrupt change in the MOC beyond the end of the 21st century cannot yet be assessed reliably. For low and medium emission scenarios with atmospheric greenhouse gas concentrations stabilized beyond 2100, the MOC recovers from initial weakening within one to several centuries. A permanent reduction in the MOC cannot be excluded if the forcing is strong and long enough.
The model projections for extremes of precipitation show larger ranges in amplitude and geographical locations than for temperature.
The response of some major modes of climate variability such as ENSO still differs from model to model, which may be associated with differences in the spatial and temporal representation of present-day conditions.
The robustness of many model responses of tropical cyclones to climate change is still limited by the resolution of typical climate models.
Changes in key processes that drive some global and regional climate changes are poorly known (e.g., ENSO, NAO, blocking, MOC, land surface feedbacks, tropical cyclone distribution).
The magnitude of future carbon cycle feedbacks is still poorly determined.
Uncertainties concerning sea levels, according to the IPCC (p.90):
Models do not yet exist that address key processes that could contribute to large rapid dynamical changes in the Antarctic and Greenland Ice Sheets that could increase the discharge of ice into the ocean.
The sensitivity of ice sheet surface mass balance (melting and precipitation) to global climate change is not well constrained by observations and has a large spread in models. There is consequently a large uncertainty in the magnitude of global warming that, if sustained, would lead to the elimination of the Greenland Ice Sheet.
Key uncertainties concerning regional projections (p.90):
In some regions there has been only very limited study of key aspects of regional climate change, particularly with regard to extreme events.
Atmosphere-Ocean General Circulation Models show no consistency in simulated regional precipitation change in some key regions (e.g., northern South America, northern
Australia and the Sahel).
In many regions where fine spatial scales in climate are generated by topography, there is insufficient information on how climate change will be expressed at these scales.
MOC: Meridional Overturning Circulation: an overturning circulation of the ocean.
ENSO: El Nino-Southern Oscillation: a coupled ocean-atmosphere phenomenon (IPCC models have consistently failed to predict changes to the naturally-appearing ENSO).
NAO: North Atlantic Oscillation: an ocean oscillation.
DTR: Diurnal temperature range: the difference between the maximum and minimum temperature during a 24-hour period.
