WASHINGTON -- A new ranking of U.S. senators based on their climate activism puts soon-to-be presidential candidate Bernie Sanders among the top "climate hawks."

The Vermont independent, who is expected to announce his presidential bid Thursday, has a score of 63 for climate leadership so far in the 114th Congress, and scored a 95 for the 113th Congress in a new ranking from the group Climate Hawks Vote. The group, a recent entrant into the fray of environmentally minded political organizations, is trying to make climate change a top issue for members of Congress. They define "climate hawks" as "people who care about climate and clean energy."

The group's ranking looks only at climate change -- not other environmental issues -- and compiles voting records, senators' history of introducing and co-sponsoring legislation, press releases and speeches they've put out on the subject, which caucuses they've joined, and what their official website says about the issue. The ranking weighs "public engagement" as the most important factor, and scores senators on a scale from -100 to +100.

Sanders has stood out on climate issues, championing solar power and regularly bashing climate change deniers.

Others atop the list are Sheldon Whitehouse (D-R.I.), who delivers weekly floor speeches on climate change. He delivered his 97th speech on Tuesday. Whitehouse has a score of 71 so far this Congress, and a 94 for the 113th Congress. Ed Markey (D-Mass.) also scored high, as did Barbara Boxer (D-Calif.) and Brian Schatz (D-Hawaii).

The ranking also dinged Democrats that the group feels have not been high performers on climate change. Chuck Schumer (D-N.Y.), who is expected to take over leadership of the Democratic caucus after the retirement of Senate Minority Leader Harry Reid (D-Nev.), scored in the 20s for every year the senators were ranked. The group criticized Schumer, arguing that he "refuses to connect the dots" when it comes to climate change and extreme weather events such as Hurricane Sandy. (He has mentioned it in press comments over the years.)

Elizabeth Warren (D-Mass.), a liberal favorite, was also criticized, scoring a 48 for the 113th Congress and a 25 so far in 2015. The scorecard notes that she's only "middle-of-the-pack" on climate. "Some Senate observers have expected Warren to discuss climate change more this year now that she is on the Energy & Natural Resources Committee, but so far she's only made one public statement, engaged in minimal press release work, not written any bills, and co-sponsored very few bills," the group wrote, adding that it hopes she will "speak out more in 2015 and beyond."



The group scored only three Republicans, all of whom have had a reputation for being better on climate and clean energy than their colleagues: Chuck Grassley (Iowa), Kelly Ayotte (N.H.) and Susan Collins (Maine), who scored -3, 1 and 6, respectively, for 2015.

While low, the scores put them ahead of six Democrats: Mark Warner (Va.), Jon Tester (Mont.), Joe Donnelly (Ind.), Heidi Heitkamp (N.D.), Joe Manchin (W.Va.) and Claire McCaskill (Mo.). Bob Casey (Pa.) tied Grassley with a -3.