http://www.ae-info.org/ae/Member/Tol_Richard


"(...)
The consensus paper by Cook et al (2013) generated a lot of interest. Consensus is not proof, but occasional stock takes of the state of scientific knowledge are useful for identifying fruitful new research avenues and potential paradigm shifts. Agreement, or perceived agreement, about the extent and causes of climate change has no bearing on rational choices about greenhouse gas emission reduction—those are driven by the trade-offs between the impacts of climate change and the impacts of climate policy—but it does affect the public perception of and the political debate on climate policy, as does the integrity of climate research. (...)"
http://iopscience.iop.org/article/10.1088/1748-9326/11/4/048001/meta



Proof is not necessary:
" 'The precautionary approach contained in Principle 15 of the Rio Declaration on Environment and Development is an approach to uncertainty, and provides for action to avoid serious or irreversible environmental harm in advance of scientific certainty of such harm.'
CBD Technical Series No. 66
Geoengineering in Relation to the
Convention on Biological Diversity:
Technical and Regulatory Matters
Part I.
Impacts of Climate-Related
Geoengineering on Biological Diversity
September 2012"
http://globalskywatch.com/chemtrails/ubbthreads.php?ubb=showflat&Number=17985#Post17985