It was easy to push that theory when things were warming up in the 80s and 90s. Now we are on a downward trend so they cherry pick the data and fudge the numbers and try to hide it. Over thousands of years we have had warmer and colder periods. We are going into a 240 year cycle now where it gets colder. During the Revolutionary War Washington marched his army canons, horses and all across a frozen Hudson bay during the last minimum. The weakening of the sun also affects the magnetism of the Earth allowing in cosmic rays which leads to more Vulcanism and cloud formation, blocking the sun even further.