But how does the world go about achieving such a lofty goal? On the 40th anniversary of Earth Day, the stream of new and innovative ways to curb carbon emissions and (hopefully) curb global warming seems never-ending these days, making it all the more difficult to figure out which environmental technologies will truly help to save the planet.
DailyFinance spoke with several environmental and clean technology experts to find out which methods they think will have the biggest impact on carbon emissions. Of course, these technologies alone won't be enough. "There's no single Holy Grail; there's no silver bullet. It's going to take many different technologies, used in thousands of creative ways, to save the planet," says Ron Pernick, principal at research firm Clean Edge.
That said, here are five of the most promising environmental technologies that could help save the planet:
Commercial solar power has been around since the 1970s, but it's only just now starting to become affordable enough to make a real impact on energy use. After a years-long supply shortage, prices have plunged in the last two years. Solar production boomed after manufacturers scrambled to add capacity during the shortage, and that led to a huge boost in supply right when the growth in solar installations began slowing thanks to the recession and slashed government subsidies.
The double whammy of the excess supply and slower growth has bought the price of solar to a total cost of less than 18 cents per kilowatt-hour in sunny climates, according to Photon Consulting. That compares to retail electricity prices that last year ranged from an average of 6.08 cents per kilowatt-hour in Wyoming to 21.21 cents per kilowatt-hour in Hawaii.
"The way the price is coming down is so extraordinary that if it keeps on this pace, solar will be a cheaper way of producing power than conventional fuels in five to 10 years," says Ethan Zindler, head of U.S. research at Bloomberg New Energy Finance. The Pew Center on Global Climate Change estimates the installation of between 200 and 400 gigawatts of new solar capacity by 2020, bringing solar up to 1.5% to 3% of total electricity output and reducing carbon emissions from electricity by 0.3% to 0.6%.
Adam Krop, vice president for equity research at Ardour Capital Investments, is still skeptical of solar's potential to catch up to fossil fuels, however. He estimates solar will likely only make up about 1% of the total global electricity generating capacity for the foreseeable future -- and that's an aggressive target. In the U.S., solar electricity accounts for only 0.01% of the total, he says, but could grow to 0.5% by 2020. That would mean rapid growth, but not enough to dramatically slash carbon emissions.
Still, Robert Wilder, CEO of WilderShares, which manages several clean-energy indexes, says while solar is not likely to exceed 4% to 5% of the world's energy supply in the next 20 years, it's got plenty of potential in the longer term. "In 50 to 100 years, I'd say, hands down, solar's the Big Kahuna," he says. "[Sunlight] is free and abundant, and could provide much more electricity than we need."
Wind power is the cheapest and the most widespread renewable energy today, providing about 1% of U.S. electricity. If wind generated 20% of the country's electricity by 2030, it would eliminate some 25% of the expected carbon-dioxide emissions, the Department of Energy says. And it's already cost-competitive with natural gas in many regions.
In the U.S., wind power costs between 6 and 13 cents per kilowatt-hour, including tax incentives, the Pew Center on Global Climate Change estimates. (Rather than selling directly to end customers, like most solar projects, wind projects usually deliver wholesale power to the grid. In 2007, the latest year for which averages are available, U.S. wholesale electricity sold for between 4.86 cents per kilowatt-hour and 7.10 cents per kilowatt-hour.)
David Jones, editor of the Platts Renewable Energy Report, thinks wind power has the potential to significantly lower carbon emissions, especially as more offshore wind projects are completed. Wind is more abundant and more consistent offshore, allowing project developers to use bigger turbines and produce electricity at lower cost, he says.
However, while wind is the most economically competitive renewable energy source today, the price for wind turbines haven't fallen much in the last five years, thanks -- in large part -- to high steel prices, Zindler says. Because wind-turbine prices haven't shown the kind of downward trend that solar prices have seen, solar may be the safer bet, he says.
The sun doesn't always shine, the wind doesn't always blow and neither of those events can be controlled by the utility companies. And that's a major -- and growing -- challenge as these renewable energies become a larger part of the energy mix.
Currently, utilities need to back up large amounts of wind power with carbon-emitting coal- or natural-gas power plants when the wind isn't strong enough to meet the electricity demand. Some companies are hoping to solve this problem with batteries and other technologies that can store huge amounts of energy for the grid.
"If you can store renewable power like that, then the main argument against renewables like solar and wind goes out the window," Jones says. Making solar and wind power dispatchable with such storage would triple the value of that power, says Maurice Gunderson, a partner at venture-capital firm CMEA Capital.
The problem is that given the large amount of storage required, these technologies are currently too expensive and don't have long-enough lifespans to make sense for utilities. The technology isn't here yet, and Gunderson says he doesn't expect a viable solution for another 10 to 15 years.
Reducing the amount of energy consumers and businesses use offers the quickest and cheapest ways to cut carbon emissions, according to U.S. Energy Secretary Steven Chu. Consulting firm McKinsey & Co. in July estimated the U.S. could cut its energy consumption from homes, businesses and factories by 23% with things like better insulation, as well as more energy-efficient lighting, heating and cooling systems, home appliances, office equipment and industrial processes. That would eliminate 1.1 gigatons of greenhouse-gas emissions annually and generate a net savings of $680 billion.
Globally, energy-efficiency measures -- including transportation -- could deliver up to half of the reduction of greenhouse-gas emissions required to meet to G8 goal, according to another McKinsey report. With buildings accounting for nearly 40% of U.S. emissions, it's clear that energy-efficiency technologies will play a key role.
In fact, energy efficiency was one of the top clean tech venture investment categories in the first quarter, accounting for the largest number of deals, especially in lighting, according to the Cleantech Group. Unlike the construction of new power plants, which are capital intensive and take a long time to sell and build, lighting investments tend to cost less -- and some investors think it'll be easier to convince customers to change a light bulb than an energy source.
Lighting technologies, such as light-emitting diodes, are easily adoptable and because of that will likely have a bigger impact than more ambitious technologies in the near term, says David Berkowitz, a general partner at venture-capital firm Ventures West. "I'm seeing a whole bunch of innovation in that area," he says. "I think we''re going to see, in the next 10 years, some significant adoption of LED lighting technologies."
Lighting comprises 19% of all of the electricity used worldwide, so more efficient lighting technologies could take a good-sized bite out of carbon emissions. But it will take a whole raft of energy-efficiency technologies to reach the G8 goal. Heating and cooling systems offer another big opportunity to cut carbon. Space heating and cooling, as well as water heating, together account for 55.2% of energy consumption in homes and 34.1% of energy use in commercial buildings.
The large potential doesn't mean it'll be easy to become more energy efficient, however. "I wouldn't underestimate the fact that we have huge amounts of energy to gain by saving energy, but I think the low-hanging fruit for energy efficiency has already been grabbed," Jones says.
No list of carbon-reduction technologies would be complete without nuclear power, say Chris Gadomski, lead nuclear analyst at Bloomberg New Energy Power. Unlike solar and wind power, nuclear power can generate steady amounts of electricity all the time. Also, nuclear-generated electricity is baseload power that could potentially replace dirty coal, which answers for 20% of the world's carbon emissions and 27% of U.S. emissions.
While it's a controversial choice, nuclear power emits no carbon and supplies far more electricity than solar or wind power – about 15% of the world's electricity, as well as 45% of the world's carbon-free electricity. "There's no comprehensive solution to addressing emissions without nuclear power," Gadomski says. "You'd be missing the world's largest source of carbon-free energy."
The Obama administration supports more nuclear power in the U.S. and big investors like Microsoft (MSFT) Chairman Bill Gates are also backing the technology. Gadomski expects global nuclear capacity will more than double by 2030, with most of that growth coming from China and India.
But make no mistake: Plenty of experts, including many environmentalists, remain highly skeptical. First of all, there's the huge upfront cost of building a nuclear plant and the related financing issues. Estimates have reached $4 billion to $6 billion per gigawatt of capacity, which would make a new plant an expensive proposition for risk-averse utilities, Gadomski says. And disposing of nuclear waste and countering safety concerns continue to pose real challenges.
Still, CMEA's Gunderson calls cheap nuclear power one of three big breakthroughs needed to solve the climate-change crisis. (The other two are grid-scale energy storage and nuclear fusion, explained below.) Researchers and entrepreneurs hope to improve nuke power's prospects with new technologies that could cut costs, improve safety and reduce nuclear waste.
One of the most promising – but farthest off – of these technologies is nuclear fusion, which combines atoms instead of splitting them, producing far more power and far less radioactive waste. "If we get fusion to work, we don't need solar or other renewable generation," Gunderson says. "But it requires fundamental breakthrough and it's a harder challenge than humankind has ever taken on. It makes Apollo look like a weekend project."