In case you are not aware, Japan is one of the last bastions of people who believe in anthropogenic (man-made) global warming. The majority of the population in Japan are quite willing to sacrifice their well-being if that reduces CO2 emission and save the mother earth.
From Yomiuri Shinbun (3/7/2012):
Secretaries-general and Diet policy committee chairmen of the Liberal Democratic Party and the New Komeito Party met on March 7, and confirmed their parties' policy to agree to 4 tax bills [submitted by the Noda administration] in the bills related to the fiscal 2012 budget including the one that will create the tax for countermeasures against global warming (environmental tax).
With their agreement, the 4 bills are likely to be passed within this month.
Meanwhile, the Diet Steering Committee of the Lower House held a meeting on March 7, and decided that the fiscal 2012 budget would be voted on in the plenary session of the Lower House in the evening on March 8. The 2012 budget is expected to pass by the majority vote from the ruling coalition. The LDP and the New Komei Party confirmed in the meeting on March 7 to oppose the budget.
The budget is going to pass anyway, so the LDP and Komeito want to make a token stand that they opposed, a gesture enough to fool people into voting for them in the future.