HAMPTON, N.H. — Former Vice President Joseph R. Biden Jr. defended his record on climate change on Monday in the face of criticism from rivals for the 2020 Democratic presidential nomination, and called for a “green revolution” that is “rational” and affordable.

During his first campaign swing in New Hampshire since entering the race for president, Mr. Biden also said that breaking up big technology companies such as Facebook is “something we should take a really hard look at,” and derided President Trump’s tariffs on Chinese goods.

Speaking at a New Hampshire pizza restaurant, Mr. Biden pledged to deliver “a major speech in detail” by the end of May outlining his environmental priorities. That promise followed an article by Reuters in which one person advising Mr. Biden described him as seeking a middle ground in the fight against the planet’s warming. The Biden campaign said that characterization was inaccurate, but liberal activists and candidates like Senator Bernie Sanders of Vermont questioned his boldness on climate.

Mr. Biden, echoing the language of revolution used by Mr. Sanders, said Monday that the nation needed “environmental revolution” and dismissed the Reuters article by citing a PolitiFact assessment of his work on the issue. The fact-checking outlet ruled last week that he had, in fact, introduced the first bill addressing climate change in the 1980s.