A number of politicians, particularly many Republicans, are questioning whether global warming is being caused by human activity. Some are now claiming that scientists are split on the issue. Politifact decided to check up on these ridiculous claims:

To begin with, a 2007 report from the U.N. Intergovernmental Panel on Climate Change, the world’s leading international scientific body on climate science, states: “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 years can be explained without external forcing, and very likely that it is not due to known natural causes alone.” (External forcing refers to anything that changes the climate that is outside of the normal climate system.)

A 2009 report from the U.S. Global Change Research Programreached a similar conclusion: “Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities.”

Current climate change research was reviewed again this year by the National Research Council and the National Academy of Sciences. The committee it assembled concluded that global warming poses significant risksand is happening primarily because of greenhouse gas emissions from human activities. It rejected the idea that those findings are in any way questionable.

“Although the scientific process is always open to new ideas and results, the fundamental causes and consequences of climate change have been established by many years of scientific research, are supported by many different lines of evidence, and have stood firm in the face of careful examination, repeated testing, and the rigorous evaluation of alternative theories and explanations,” the committee’s report said.

The scientific consensus on global warming is clear.

This is a very encouraging story. Serious early-stage investors are taking a close look at what many are calling Agriculture 2.0. Trends like urban farming have tremendous potential, and innovative trends like that can accelerate with the backing of Silicon Valley.

“Sustainable agriculture is a space that looks as big or bigger than clean tech,” said Paul Matteucci, a venture capitalist with U.S. Venture Partners in Menlo Park, Calif. “Historically, we have not seen a ton of entrepreneurial activity in agriculture, but we are beginning to see it now, and the opportunities are huge.”

A catch-all phrase for environmentally beneficial farming, sustainable agriculture has long been the province of organic enthusiasts. But venture capitalists say a growing awareness of conventional agriculture’s contribution to climate change and concerns over its consumption of water and energy are creating markets for technological innovation to minimize those effects.

The Johnny Appleseed of what is being called Agriculture 2.0 is a 33-year-old former Wall Street investment banker named Janine Yorio. Her New York firm, NewSeed Advisors, brings together sustainable agriculture entrepreneurs and investors.

At the Four Seasons hotel in East Palo Alto, Calif., last month, NewSeed Advisors attracted a crowd of well-dressed investors from some of Silicon Valley’s top venture capital firms. They packed a ballroom to hear entrepreneurs pitch start-ups developing everything from nontoxic pesticides and analytical tools for soil analysis to indoor urban farming systems.

I think the urban farming trend in particular has huge potential, particularly in Rust Belt cities like Detroit and Cleveland.

Democrat John Kerry and Republican Lindsey Graham don’t agree on much. The above photo from FOX News Sunday shows the two Senators sparring in the fall of 2008.

The two Senators, however, have teamed up to write a compelling Op-Ed in today’s New York Times in which they argue for a bi-partisan approach to addressing climate change legislation. This is a must-read for anyone who cares about this issue, and it could offer some real momentum for an issue that many believe will be stalled in the Senate.

If Lindsey Graham is on board, one would think that he could bring along more Republicans. One reason Graham is on board, and there’s hope to bring along more Republicans, is the emphasis on using nuclear power as one of the options. The left needs to become pragmatic over nuclear power, and realize that it offers the key to obtaining broad support.

Kerry and Graham also signal that a compromise is needed on domestic drilling. The clean energy revolution will not happen over-night, and if we need to rely in the short term on some fossil fuels, it’s better for the U.S. economy to use more domestic oil. We certainly shouldn’t subsidize it, but in the context of a carbon tax or cap-and-trade, permitting more domestic production makes tons of sense, particularly given the current economic crisis.

Hopefully, this can be the starting point for a grand bargain on energy.

George Soros is getting serious about climate change.

Billionaire George Soros, looking to address the “political problem” of climate change, said he will invest $1 billion in clean-energy technology and create an organization to advise policy makers on environmental issues.

Soros, the founder of hedge fund Soros Fund Management LLC, announced the investment in Copenhagen yesterday at a meeting on climate change sponsored by Project Syndicate. The group is an international association made up of 430 newspapers from 150 countries.

“I want to apply rather stringent criteria to the investments,” said Soros in an e-mailed message. “They should be profitable but should also actually make a contribution to solving the problem.”

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Soros has said he prefers a greenhouse-gas tax because carbon emission-trading systems, which are used in Europe, can be manipulated by investors.

It will be interesting to see if the advocacy by Soros helps to tip the debate in the U.S. towards a carbon tax as opposed to cap-and-trade.