Whilst technically a car has more power in colder air because the relative density of colder air is greater and therefore contains more
oxygen than warm air, it should not cause the behavior you describe.
The 2009 State of the Climate report gives these top indicators: humans emitted 30 billion tons of of CO2 into the atmosphere each year from the burning of fossil fuels (oil, coal, and natural gas), less
oxygen in the
air from the burning of fossil fuels, rising fossil fuel carbon in corals, nights
warming faster
than days, satellites show less of the earth's heat escaping into space, cooling of the stratosphere or upper atmosphere,
warming of the troposphere or lower atmosphere, etc..