The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society. Accumulating data from across the globe reveal a wide array of effects: rapidly melting glaciers, destabilization of major ice sheets, increases in extreme weather, rising sea level, shifts in species ranges, and more. The pace of change and the evidence of harm have increased markedly over the last five years. The time to control greenhouse gas emissions is now.
The atmospheric concentration of carbon dioxide, a critical greenhouse gas, is higher than it has been for at least 650,000 years. The average temperature of the Earth is heading for levels not experienced for millions of years. Scientific predictions of the impacts of increasing atmospheric concentrations of greenhouse gases from fossil fuels and deforestation match observed changes. As expected, intensification of droughts, heat waves, floods, wildfires, and severe storms is occurring, with a mounting toll on vulnerable ecosystems and societies. These events are early warning signs of even more devastating damage to come, some of which will be irreversible.
); that said, though, in most situations you can't measure the difference, and bridges built based on Newtonian mechanics mostly still don't fall down, at least not because the design was wrong. But the vast majority of scientific theories just work, and keep on working. Archimedes' "Eureka", that solids displace an equivalent volume of liquids, led to understanding of when things float or don't, to understanding density, to all sorts of things, and that theory has survived unchanged and unchallenged for 2.5 millennia. Quantum theory works! If you want to dispute that it is correct, please give back your DVD player, LED/LCD screen and Internet connection. Now, we actually know that Quantum theory and Gravity theory are currently irreconcilable! One, or probably both, still need to be refined. But that doesn't make them wrong, or make their predictions incorrect.
