Australian Broadcasting Corporation: Australians are spending more than $44 million a year to offset the carbon pollution from activities such as flights and road trips. While the Rudd Government has promised to introduce a national standard for carbon offsets by the end of this year, consumer and environment groups have developed their own ranking system. Dozens of companies sell carbon offsets to consumers in search of a clearer conscience. For a price, the companies promise to plant trees, or invest in …