The document, known as the Fairbanks Declaration, concluded Tillerson's chairing of a meeting of the Arctic Council, a board made up of indigenous groups and the eight countries bordering the Arctic, in Fairbanks, Alaska.
While the council only has the power to issue advisories, the language in the statement signed by Tillerson comes in stark contrast to statements and promises made by President Trump about climate change.
Trump has repeatedly called into question the science behind climate change, even calling it a "very expensive hoax." During his 2016 campaign, Trump promised to pull out of the Paris accord and his administration has ordered cuts to funding for climate science and has slashed environmental regulations.
While Tillerson endorsed the Arctic Council document, he cautioned that the U.S. would not be rushed into formulating its policy.
"We're not going to rush to make a decision. We're going to work to make the right decision for the United States," he said.
The Trump administration has not come out with a decision on whether the U.S. will pull out of the Paris Climate accord signed under President Obama. That non-binding international agreement went into effect last year and calls for countries to set goals for reducing greenhouse gas emissions.
The Fairbanks proclamation says that "the Arctic is warming at more than twice the rate of the global average, resulting in widespread social, environmental, and economic impacts," and notes "the pressing and increasing need for mitigation and adaptation actions and to strengthen resilience."
Later in the statement, the parties commit a whole section to addressing the impacts of climate change, laying out eleven steps forward.
The State Department defended Tillerson's signing by saying the declaration is not an obligatory document.
"The Fairbanks Declaration notes what Paris claims to be," a State Department official told ABC News. "It does not obligate the U.S. to enforce it."
The Canadian foreign minister thanked the U.S. delegation for signing the document today.
"We came to a really good place in our statement, and I think that says something really important to the world," said Chrystia Freeland, addressing the Americans. "I know that that took some effort to get there, so thank you very much."
The assent to the Arctic Council's declaration comes as the Trump administration has a delegation in Germany to attend U.N. climate talks, a follow-up to the Paris agreement focused on implementation.
During his confirmation hearing, Tillerson said he had concluded as a scientist and engineer that "the risk of climate change does exist" and that "action should be taken." But, he added, "Our ability to predict that effect [of climate change] is very limited," and offered little detail on what those steps should be.