A group of scientists has published a letter in the journal Science defending climate science and, in particular, the evidence for climate change, from recent attacks and harassment. The entire letter is worth reading, but here is the key part to keep in mind:
But there is nothing remotely identified in the recent events that changes the fundamental conclusions about climate change:The scientists do not offer specifics on each of those points, but plenty of websites do. I would suggest the lists answering common contrarian arguments at Skeptical Science and New Scientist if you are interested in more detail.
(i) The planet is warming due to increased concentrations of heat-trapping gases in our atmosphere. A snowy winter in Washington does not alter this fact.
(ii) Most of the increase in the concentration of these gases over the last century is due to human activities, especially the burning of fossil fuels and deforestation.
(iii) Natural causes always play a role in changing Earth's climate, but are now being overwhelmed by human-induced changes.
(iv) Warming the planet will cause many other climatic patterns to change at speeds unprecedented in modern times, including increasing rates of sea-level rise and alterations in the hydrologic cycle. Rising concentrations of carbon dioxide are making the oceans more acidic.
(v) The combination of these complex climate changes threatens coastal communities and cities, our food and water supplies, marine and freshwater ecosystems, forests, high mountain environments, and far more.
Much more can be, and has been, said by the world's scientific societies, national academies, and individuals, but these conclusions should be enough to indicate why scientists are concerned about what future generations will face from business-as-usual practices. We urge our policy-makers and the public to move forward immediately to address the causes of climate change, including the unrestrained burning of fossil fuels.