Although the world's governments meeting in Copenhagen struggled to agree on a plan of action to curtail carbon dioxide emissions, the green technology innovations reported by New Scientist during 2009 suggest reasons for optimism.
Transport continued to be a big target for green ideas despite tough economic times. In the US the sector is the second largest contributor to emissions, responsible for 28 per cent of the country's total. Of those, 60 per cent are from road vehicles â€“ indeed, a study this year concluded that the average fuel efficiency of the US vehicle fleet has risen by just 1.3 kilometres per litre (3 miles per gallon) since the days of the Ford Model T.
That looks set to change soon though. A wide range of possible solutions were on show in Las Vegas, Nevada, last month as the teams competing in this year's Automotive X Prize were announced. The prize challenges teams to make a production-ready vehicle able to travel 100 miles on the equivalent energy of a gallon of petrol. See a gallery of teams taking part,
It's been a good year for the electric car. Governments bailed out the largest auto companies with the proviso that they pump resources into battery-operated vehicles , and as a result 2009 was the year that battery chemistry became cool. Such is the buzz around electric cars that some researchers are even developing ways to convert gas guzzlers to electricity.
Hydrogen or methanol?
Elsewhere, the quest to power transport using hydrogen continued. One team showed that existing gas power stations could be easily modified to pump out hydrogen, but transporting and storing hydrogen still pose major technological hurdles.
Perhaps the methanol economy is more achievable â€“ the alcohol is a liquid at room temperature, like petrol, so the existing infrastructure could be easily adapted, according to some.
Ways to make the aviation industry leaner and greener were also on show in 2009. They included the suggestion that aircraft wing tips could morph mid-flight to give extra lift and cut fuel consumption.
But greening air travel is also about land operations. Plane manufacturer Airbus started to investigate if robotic trucks to tow aircraft could reduce the $7 billion and 18 million tonnes of CO2 that result from using jet engines designed for flight to trundle from runway to terminal and back.
Of course, finding ways to avoid travel â€“ videoconferencing, for example â€“ will also cut transport emissions. A system to project your animated features onto a blank-faced dummy was one method suggested to make virtual travel closer to the real thing.
But sending data through the internet has a carbon footprint of its own. Spam is not only an inconvenience to the individual, but globally produces emissions equivalent to burning 9 billion litres of petrol annually. Yahoo's proposed email postage stamp system could take a chunk out of the net's carbon footprint â€“ if users can be persuaded to start giving money for charity for every email they send.
IBM and Google also unveiled plans to cut the environmental damage done by internet infrastructure, but individual web users could have their own part to play in creating a green internet. One of the world's biggest manufacturers of routers is trialling a system to store some web data in the homes of broadband subscribers to cut the power use of the huge data centres on which the internet currently relies.