The Smithsonian has already acknowledged one error in handling Dr. Soon.

Charles R. Alcock, director of the Harvard-Smithsonian Center for Astrophysics, said last week that a contract provision with funders of Dr. Soon’s work that appeared to prohibit disclosure of funding sources “was a mistake.”

“We will not permit similar wording in future grant agreements,” Dr. Alcock said in an email response to questions.

Dr. Soon has taken a view, contrary to the vast majority of climate scientists, that variations in sunlight may account for much of the recent warming of the earth. The Smithsonian has long distanced itself from Dr. Soon, stating that it does not share his conclusions about climate change, but allowed him to continue working at the Center for Astrophysics, a joint operation with Harvard that is based in Cambridge, Mass.

After news of the letters from Representative Grijalva was announced, Professor Pielke wrote on Twitter, “Climate McCarthyism alive & well. Just learned a U.S. congressman has contacted my university to ‘investigate’ me.”

Professor Pielke went on to note in the tweet that “I’m not even a skeptic” and that he supports the conclusions of the United Nations committee that reviews climate science, as well as the Obama administration’s proposed Environmental Protection Agency regulations on greenhouse gases. He has, however, expressed frequent criticism of climate scientists.

Professor Pielke also noted in a post on his blog that in 2010 he denounced the efforts of Kenneth T. Cuccinelli II, then the attorney general for Virginia, to investigate the emails and papers of the climate scientist Michael Mann.

On his blog, Professor Pielke said that the pressure and “smears” had caused him to move away from climate research: “I am simply not initiating any new research or papers on the topic and I have ring-fenced my slowly diminishing blogging on the subject.” In an email response to questions, he said he had “unequivocably, never“ taken money from the fossil fuel companies or allied organizations.