As we round the corner into 2008, its worth taking a look back on what might easily be considered the year climate change got really, well, hot. From Al Gore's Inconvenient Truth to the Nobel Peace Prize to the Bali roadmap, global warming picked up a lot of press, often from unexpected quarters. So what were the key climate stories of 2007? For me, the real winners are the stories that foreshadow new developments in science, technology, politics, and innovation. Here are my top five picks , and why they still deserve your attention. By Will Sarni

1. Tesco becomes the first supermarket chain in the world to assign "carbon labels" to every product on its shelves.

The story: In January, the U.K.s largest retail chain mandates that store labels will record the amount of carbon dioxide emitted during the production, transport, and consumption of each of its 70,000 products. "The market is ready," says Sir Terry Leahy, Tesco's chief executive. "Customers tell us they want our help to do more in the fight against climate change. We have to make sustainability a significant, mainstream driver of consumption."

Why it's important: The retail sector (including Wal-Mart) is moving suppliers to think about the lifecycle impact of their products. This will contineu to be used as a competitive advantage in the marketplace.

2. Green-minded investors buy out TXU.

The story: Kohlberg Kravis Roberts & Company and the Texas Pacific Group propose a record $45 billion buyout of TXU, including a goal to lower the utilitiy's carbon dioxide emissions to 1990 levels by 2020. The environmental commitment comes through a highly unusual process in which the equity firms ask prominent environmental groups what environmental measures could be taken to win their support. The deal

Why it's important: The influence of environmental issues on an acquisition of this scale is unprecedented. We're now seeing additional pressure from utility regulatory commissions and state regulatory agencies to counter "business as usual" in regard to approving coal-fired plants. For example, the Indiana Utility Regulatory Commission approved a $2 billion coal-fired plant by Duke Energy but required them to come up with a plan within six months to sequester carbon dioxide. In addition, coal-fired plants in Wyoming, Kansas, and Washington State were recently denied due to global warming concerns. Despite the relentless building of coal-fired plants in China, the U.S. is exerting its influence at the state level to restrict coal-fired plants on home soil.

3. The U.S. Conference of Mayors and the State of California take the lead in reducing greenhouse gas emissions.

The story: Six hundred mayors sign the U.S. Conference of Mayors Climate Protection Agreement, in which they pledge to reduce carbon dioxide emissions by 7% below 1990 levels by 2012. This agreement is the only climate protection agreement of its kind among U.S. elected officials.

Why it's important: Local governments are picking up the slack from federal regulators. Watch for the private sector to lobby for federal leadership and consistency in the emerging regulatory framework.

In December, the U.S. EPA denied a waiver that would have given California the right to regulate vehicle emissions. The state will have to look elsewhere to meet its self-imposed mandate to reduce 173 million tons of CO2 by 2020. In the meantime, 15 other states have joined California's legal challenge of the EPA ruling.

4. The opening of the Northwest Passage stir up geopolitical concerns.

The story: The Russians plant a flag on the Arctic seabed, the Canadians hold military maneuvers in the Arctic to assert its claim of sovereignty, and the U.S. reconsiders ratifying the Law of the Sea treaty to protect its nearly 1,000 miles of coastline in the Arctic. Countries vie to dominate the Arctic as the Northwest Passage becomes navigable and to stake claim to potential oil and gas reserves.

Why it's important: These incidents offer an unsettling glimpse into the political implications of a warming planet.

5. Al Gore and the IPCC share the Nobel Peace Prize for climate change work.

The story: Former Vice President Al Gore and the IPCC share the 2007 Nobel Peace Prize. Rajendra Pachauri, the Indian climatologist who heads the IPCC panel, announces that science had won out over skepticism. Al Gore and the IPCC are praised by the Nobel Committee for their efforts to build up and disseminate greater knowledge about man-made climate change.

Why it's important: It's gotten everyones attention, including the skeptics (if any remain). Most importantly, the award is a validation for the United Nations panel, which in its early days was vilified by those who disputed the scientific case for a human role in climate change.

Other stories of note...

• The Bali roadmap. Two years of more talks significant because of the commitment to talk, but disappointing as well.
• The departure of incandescent bulb. The U.S. has four years (by 2012) to replace incandescent light bulbs. Products are being legislated out of use not for safety concerns but also because of energy use and carbon emissions. Climate change will create opportunities for new products and services unimagined in 2007.
• RECs and carbon credits in question. Voluntary standards emerge as buyers and NGOs question the quality of offset credits. This is part of the next phase of the carbon market rigor.
• Record investment in clean technology. VC investment in clean energy technology topped $100 billion in 2007. Investment will continue as innovation drives new products and services.

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Will Sarni is CEO of sustainability consulting firm DOMANI. He is also SLM's expert-in-residence on climate strategy and the host of Climate Management Weekly.