Large-scale changes in Earth's climate
A climate contrarian named Alec Rawls claimed, on the basis of a single sentence in a leaked draft of the Fifth Assessment Report (FAR), the entire edifice of climate science is about to collapse. In his interpretation, the Intergovernmental Panel on Climate Change is about to acknowledge the validity of a longstanding fringe theory: that cosmic rays have a huge influence on the earth's climate.
"The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized G.C.R. (galactic cosmic rays)-cloud link."
So far virtually all scientific research on GCRs has shown that they are not effective at seeding clouds and thus have very little influence over the Earth's temperature. The leaked IPCC report specifically states this: "... (T)here is medium evidence and high agreement that the cosmic ray-ionization mechanism is too weak to influence global concentrations of [cloud condensation nuclei] or their change over the last century or during a solar cycle in any climatically significant way."
Steve Sherwood, a climate scientist at the University of New South Wales is a lead author of the chapter in question. "The single sentence that this guy pulls out is simply paraphrasing an argument that has been put forward by a few controversial papers purporting significant cosmic-ray influences on climate. Its existence in the draft is proof that we considered all peer-reviewed literature, including potentially important papers that deviate from the herd. The rest of the paragraph from which he has lifted this sentence, however, goes on to show that subsequent peer-reviewed literature has discredited the assumptions and/or methodology of those papers, and failed to find any effect. The absence of evidence for significant cosmic-ray effects is clearly stated in the executive summary. This guy's spin is truly bizarre. Anyone who would buy the idea that this is a 'game changer' is obviously not really looking at what is there."
The draft report says it is "virtually certain" that greenhouse gases released by human activities are causing an energy imbalance that is warming the earth, and finding "very high confidence" that natural drivers of climate change are causing only a small fraction of that imbalance. Assuming the draft language remains unchanged, this will be the single most important FAR conclusion: "It is extremely likely (95 percent) that human activities have caused more than half of the observed increase in global average surface temperature since the 1950s. There is high confidence that this has caused large-scale changes in the ocean, in the cryosphere, and in sea level in the second half of the 20th century. Some extreme events have changed as a result of anthropogenic influence."
An ad from the Marijuana Policy Project claims marijuana is "less toxic" than alcohol. Politifact focused on whether the drug in its natural form is "less toxic" than alcohol. In that regard, science and statistics present a strong case: deaths or even trips to the hospital are much more likely due to alcohol; scientists could not find any documented deaths from smoking marijuana; a study found that marijuana is 100 times less toxic than alcohol.
Experts say one concern is the impact of marijuana on the brain, particularly for teens who start smoking early. A study on 1,037 individuals followed from birth until age 38 determined those who began using cannabis before age 18 and became persistent users (more than once a week) suffered a decline in IQ (an average of eight IQ points) that didn't improve once they stopped.