The UN summit, also known as the COP26 summit, is set to bring together more than 100 heads of state, including Moon, US.
President Joe Biden and British Prime Minister Boris Johnson, in Glasgow, Scotland's biggest city.
World leaders are expected to assess achievements since the Paris agreement to limit global warming, which was signed in 2015.
Whether to agree on limiting global warming to 1.5 degrees Celsius is one of the key topics at the UN summit.
Scientists said the timing of the 1.5 C rise in the earth's temperature is very likely to come before 2040, a decade faster than an earlier prediction, if greenhouse gas emissions remain at current levels.
During the summit, Moon plans to deliver a keynote speech on South Korea's efforts for carbon neutrality.
Earlier this month, South Korea finalized a decision to reduce its greenhouse gas emissions by 40 percent from the 2018 levels by 2030, sharply raising its previous goal as part of efforts to curb the pace of climate change.
South Korea also confirmed that it will achieve carbon neutrality by 2050, as the nation started tackling the challenge of responding to climate change and attaining sustainable growth simultaneously.
South Korea's decision to reduce emissions will be reported during the COP26 talks, officials said.
Britain is the second leg of Moon's three-nation swing through Europe that already took him to Italy for a G-20 summit and will include a state visit to Hungary later this week. (Yonhap)