Robust Findings and Key Uncertainties - IPCC 2007 Synthesis Report.

Reposted from: http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf

I have noted below some of the Robust Findings and Key Uncertainties in Section 6 of the IPCC 2007 Synthesis Report.

6.1 Observed changes in climate and their effects, and their causes

Robust findings

• Warming of the climate system is unequivocal
• Global total annual anthropogenic GHG emissions have grown by 70% between 1970 and
  2004
• Most of the global average warming over the past 50 years is very likely due to anthropogenic GHG increases

Key uncertainties

• Analysing and monitoring changes in extreme events, including drought, tropical cyclones, extreme temperatures and the frequency and intensity of precipitation, is more difficult than for climatic averages

6.2 Drivers and projections of future climate changes and their impacts
Robust findings

• With current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next few decades.
• For the next two decades a warming of about 0.2°C per decade is projected for a range of SRES emissions scenarios.
• Continued GHG emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.

Key uncertainties

• Models differ considerably in their estimates of the strength of different feedbacks in the climate system, particularly cloud feedbacks, oceanic heat uptake and carbon cycle feedbacks
• Future changes in the Greenland and Antarctic ice sheet mass, particularly due to changes in ice flow, are a major source of uncertainty that could increase sea level rise projections.
• Decisions about macro-economic and other policies that seem unrelated to climate change can significantly affect emissions.

6.3 Responses to climate change
Robust findings

• Some planned adaptation (of human activities) is occurring now; more extensive adaptation is required to reduce vulnerability to climate change.
• Unmitigated climate change would, in the long term, be likely to exceed the capacity of natural, managed and human systems to adapt.
• The economic mitigation potential is sufficient to offset the projected growth of global
  emissions or to reduce emissions to below current levels in 2030.
• Many impacts can be reduced, delayed or avoided by mitigation.
  
• Delayed emissions reductions significantly constrain the opportunities to achieve lower stabilisation levels and increase the risk of more severe climate change impacts.
• The range of stabilisation levels for GHG concentrations that have been assessed can be achieved by deployment of a portfolio of technologies that are currently available

Key uncertainties

• Barriers, limits and costs of adaptation are not fully understood
• Estimates of mitigation costs and potentials depend on assumptions about future socio-economic growth, technological change and consumption patterns.