From the viewpoint of a skeptical former Sierra Club activist and USEPA senior analyst

Aug. 19, 2016 – Alan Carlin

Climate alarmism is probably the greatest hoax/scam in world history. The main evidence for catastrophic anthropogenic global warming (CAGW), the principal alleged adverse effect of human emissions of carbon dioxide (CO2), is climate models built by CAGW supporters in a field where models with real predictive power do not exist and cannot be built with any demonstrable accuracy beyond a week or two because climate and weather are coupled non-linear chaotic systems. Without the models, the whole hoax/scam collapses. Even the Intergovernmental Panel on Climate Change (IPCC) has stated (see Section 14.2.2.2 of the 2001 IPCC Report):

In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that long-term prediction of future climate states is not possible.
Climate Modelers Knew…