Last week began with a Supreme Court decision declaring that the federal government had the authority to regulate greenhouse gas emissions and all but ordering the Bush administration to do so. It ended with a report from the Intergovernmental Panel on Climate Change — the world’s authoritative voice on global warming — warning that failure to contain these emissions will have disastrous environmental effects, especially in poorer countries, which are least able to defend themselves and their people against the consequences of climate change. One would hope that these events would shake President Bush out of his state of denial and add his authority to the chorus of governors, legislators and business leaders calling for an aggressive response to the dangers of global warming. They haven’t. When asked about the Court decision, the president said he thought he was already doing enough.

The panel’s next paper will discuss alternatives to business as usual. These policies will almost certainly require a major shift in the way energy is produced and used, as well as massive investments in new technologies. They will also be expensive. But what the world’s scientists are telling us, with increasing confidence, is that the costs of doing nothing will be far greater than the costs of acting now.