Climate with Logic

If everyone in the world wanted winter to be warmer and agreed to a plan to move the thermometer up a few degrees, what would the plan be to implement this deliberate warming? You see there is nothing humanity can do collectively to warm the earth up a few degrees even if everyone on earth made a concerted effort to do so. Weather changes constantly, and climate changes from Ice Ages to droughts, but man is not able to manipulate the climate that is controlled by forces larger and more powerful than all humanity.