The United Nations summit was due to take place in Glasgow this month but has been postponed until November next year as a result of the global coronavirus crisis.
Activists staged a protest outside Glasgow Science Centre on Friday and welcomed the boat as it sailed up the River Clyde after setting off from Fairlie in North Ayrshire.
They carried signs with messages such as "The End is Nigh", "Climate Justice, Just Transition, an End to Indecision" and "Climate Struggle = Class Struggle".
Protesters chanted "What do we want? Climate justice. When do we want it? Now" as they welcomed the boat, named Saorsa, which was emblazoned with a banner stating "Same Storm. Different Boats."
The event launched From The Ground Up: Global Gathering For Climate Justice, a weekend of online events organised by the COP26 Coalition with the aim of giving a platform to activists from across the world.
Quan Nguyen, an organiser of the From The Ground Up Gathering, said: "We may all be in the same storm but we are patently not in the same boat.
"As we face a multitude of colliding crises - Covid-19, the incoming recession, climate breakdown, racism, hunger, poverty, the mass displacement of peoples - this gathering will bring together grassroots movements who are speaking truth to power around the world.
"We urge everyone to join us in organising against these root causes in the lead up to the UN climate negotiations in Glasgow 2021."