A train splashed with a green stripe carried 450 U.N. officials, delegates, climate activists and journalists from Brussels to the climate summit in Copenhagen on Saturday to symbolize efforts to reduce the convention's carbon footprint.
More trains were leaving from other European capitals, and one was concluding a trip from Kyoto, Japan, through China and the Trans-Siberian route across Russia.
But symbols were all the trains could be. Most of the 15,000 people expected at the two-week conference opening Monday will arrive by plane from opposite ends of the globe.
The journey through Belgium, Germany and Denmark was intended to underscore what campaigners say is the need to switch to low-carbon economies and rely more on public transportation to reduce tailpipe emissions.
"Anyone who thinks it's impossible is wrong," said Achim Steiner, director of the U.N. Environment Program, noting Germany's move away from fossil fuels over the past 10 years toward greater use of wind, solar and hydroelectricity.
Railway officials claimed the trip is carbon neutral. They said the German railroad, Deutsche Bahn, bought the equivalent of the electricity needed to run the train from renewable sources and added it to the Germany electrical grid.
Traveling by train along the nearly 500-mile (800-kilometer) route emits 33 kilograms of carbon dioxide per person, compared with 115 kilograms by air, the officials said.
Led by France, high-speed rail is being extended through much of Europe, with trains moving faster than 155 miles per hour (250 kph). Airlines say they plan to link up with railways to provide alternatives to short European flights.
But train travel is still not glitch-free. A power problem in moving from the Belgian to the German grid delayed the Climate Express by a half-hour at the German border town of Aachen, although railway officials said the transfer problem was unusual and the lost time would be made up.
The 14-hour journey passed rolling hills of eastern Belgium and German farmland and industrial centers. That compared with three hours' flight and about nine hours by car _ in the unlikely case there are no traffic jams on Europe's crowded highways.
Steiner called for more investment in public transport and green energy, saying that business investors were looking for signals emerging from the summit.
"Hundreds of billions of dollars are in waiting mode," he said. "In this financial crisis right now, Copenhagen should be one of the biggest stimulus packages."
The summit aims to draw up a political accord among 192 countries for controlling global greenhouse gas emissions causing the warming of the earth. Transportation is responsible for about 27 percent of worldwide emissions.