1) There has been global warming over the last several decades. The ocean is the component of the climate system that is best suited for quantifying climate system heat change. The warming has been less than predicted by the multi-decadal global model predictions.
2) The use of a global annual average surface temperature is an inadequate metric to quantify global warming and cooling. The documentation of the poor siting quality over land is one reason it is such a poor metric.
3) The involvement of citizen scientists to document the siting quality is a very significant achievement
4) The human addition to CO2 into the atmosphere is a first-order climate forcing. It is the largest annual-global averaged positive human radiative forcing
5) However, global warming is not equivalent to climate change. Significant, societally important climate change, due to both natural- and human- climate forcings, could occur even without global warming or cooling.
I propose these definitions be adopted in our statement
“Global Warming” is an increase in the global annual average heat content measured in Joules.
“Climate Change” is any multi-decadal or longer alteration in one or more physical, chemical and/or biological components of the climate system.
6) The correct summary statement on climate, in my view, is that
Natural causes of climate variations and changes are important. In addition, the human influences are significant and involve a diverse range of first-order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.7) Natural variations and longer term change have been significantly underestimated. Also, climate prediction is an initial-value problem
In addition to greenhouse gas emissions, these other first-order human climate forcings that are important to understanding the future behavior of Earth’s climate are spatially heterogeneous and include the effect of aerosols on clouds and associated precipitation, the influence of aerosol deposition (e.g., black carbon (soot), and reactive nitrogen), and the role of changes in land use/land cover. Among their effects is their role in altering atmospheric and ocean circulation features away from what they would be in the natural climate system. As with CO2, the lengths of time that they affect the climate are estimated to be on multidecadal time scales and longer.
8) Attempts to significantly influence impacts from regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose. With respect to CO2 [and for all other human climate forcings], the emphasis should be on supporting technological developments to mitigate these threats
9) Policymakers should look for win-win policies in order to improve the environment. The costs and benefits of the regulation of the emissions of CO2 into the atmosphere need to be evaluated together with all other possible environmental regulations. The goal should be to seek politically and technologically practical ways to reduce the vulnerability of the environment and society to the entire spectrum of human-caused and natural risks including those from climate.
10) Global and regional climate models have not demonstrated skill at predicting multi-decadal changes in climate statistics on regional and local climate in hindcast studies
11) What we recommend in our Pielke et al (2012) paper in terms of an approach to mitigation and adaptation is, as written in its abstract,
“We discuss the adoption of a bottom-up, resource-based vulnerability approach in evaluating the effect of climate and other environmental and societal threats to societally critical resources. This vulnerability concept requires the determination of the major threats to local and regional water, food, energy, human health, and ecosystem function resources from extreme events including climate, but also from other social and environmental issues. After these threats are identified for each resource, then the relative risks can be compared with other risks in order to adopt optimal preferred mitigation/adaptation strategies.And finally:
This is a more inclusive way of assessing risks, including from climate variability and climate change than using the outcome vulnerability approach adopted by the IPCC. A contextual vulnerability assessment, using the bottom-up, resource-based framework is a more inclusive approach for policymakers to adopt effective mitigation and adaptation methodologies to deal with the complexity of the spectrum of social and environmental extreme events that will occur in the coming decades, as the range of threats are assessed, beyond just the focus on CO2 and a few other greenhouse gases as emphasized in the IPCC assessments.”
When I return, I look forward to assessing further the above issues, and also invite readers on my weblog to submit guest posts to appear after I am back, which refute any of the above conclusions.