On the former subject, I recommend a short note by four Yale professors describing just where we stand in our understanding of climate change. It provides a good geological perspective to charges that earth's climate has always been changing: it has, but not at the pace we are experiencing today.
From "The Big Picture":
"However, Earth’s history has something to say about climate sensitivity and the role of carbon dioxide, as well.
The reconstruction of Earth’s history reveals a story of slow and rapid climate change and clear evidence for immense variations in temperature. While most discussions in the popular press focus on the past 100 to a few 100,000 years and the precise relationship between carbon dioxide and temperature, it is informative to examine the full range of climate variations over millions of years.
Earth was, in fact, ice-free for most of its history. For example, Earth was much warmer and had no significant polar ice between 65 to about 34 million years ago. Fifty-five million years ago, rapid and massive releases of carbon acidified the oceans and warmed Earth’s surface about 5 degrees Celsius above what was already a warm planet. At peak warming, about 50 million years ago, crocodiles roamed the Arctic amongst subtropical flora and fauna, even though the Sun’s intensity was lower than today. Much higher carbon dioxide during this time is revealed by various paleoclimate reconstructions, and subsequent global cooling is shown to have followed carbon dioxide decline.
Earth’s history tells us that the leading driver of climate change is the concentration of atmospheric carbon dioxide. Not the only driver, but the leading one. It also reveals that climate sensitivity to carbon dioxide is possibly much higher than discussed in policy-making circles. About five million years ago, carbon dioxide was as high or only slightly higher than 2009 values, and Earth reached temperatures 4 degrees Celsius warmer than now, with sea levels tens of meters higher. The present-day location of Yale University was underwater.
Many lines of evidence and study tell us about the effects of carbon dioxide release. In the past, large increases in carbon dioxide corresponded to major warming events. It is unwise to think that today’s increase in carbon dioxide will, for some reason, produce a different outcome."
As to the idea of "manufactured doubt", recall the kinds of things that went on with the connection of smoking with cancer in the 1960's, and concerns about the decline of the ozone layer in our upper atmosphere in the 1970's and 1980's. It's happening again with the political battle (not the scientific debate) over the cause of global warming. For a good review of how to politically manufacture doubt about scientific research, check out this article at the Weather Underground:
"The history of the Manufactured Doubt industry provides clear lessons in evaluating the validity of their attacks on the published peer-reviewed climate change science. One should trust that the think tanks and allied "skeptic" bloggers....will give information designed to protect the profits of the fossil fuel industry. Yes, there are respected scientists with impressive credentials that these think tanks use to voice their views, but these scientists have given up their objectivity and are now working as lobbyists. I don't like to call them skeptics, because all good scientists should be skeptics. Rather, the think tanks scientists are contrarians, bent on discrediting an accepted body of published scientific research for the benefit of the richest and most powerful corporations in history. Virtually none of the "sound science" they are pushing would ever get published in a serious peer-reviewed scientific journal, and indeed the contrarians are not scientific researchers. They are lobbyists. Many of them seem to believe their tactics are justified, since they are fighting a righteous war against eco-freaks determined to trash the economy."
Of course, don't take my word for it. Do some research yourself, and not just from politically motivated sources. Global warming is clearly already affecting our planet, from massive ice loss from Antarctica, Greenland, and the mountain ranges around the planet, earlier and earlier springs, movement of species to higher latitudes and altitudes, larger and more intense wildfires in places like Australia and the western United States, and crippling droughts.