WASHINGTON — At a joint news conference here Tuesday with President François Hollande of France, President Obama veered from his focus on the terrorist attacks in Paris to bring up the huge international gathering beginning in the French capital on Monday to hammer out a global response to climate change.

“What a powerful rebuke to the terrorists it will be when the world stands as one and shows that we will not be deterred from building a better future for our children,” Mr. Obama said of the climate conference.