Numerous studies have shown that cars are a major contributor of greenhouse gases in the atmosphere which are a cause of climate change. In the United States alone, exhaust from cars and trucks are the cause of about 20 percent of all emissions in the country. Most of this comes directly from the tailpipes of the vehicles when gasoline is burned in the car's engine. Some also comes from the petroleum extraction and delivery process itself. One gallon of gas burned in a car's engine directly produces around 19 pounds of carbon dioxide. Carbon Dioxide rises into the atmosphere and prevents heat from escaping the planet, leading to rising climate temperatures overall.
There are other ways that cars destabilize the climate as well. The manufacturing process itself has huge environmental impacts as the materials needed to produce a car (metals, plastics, rubber, glass, various chemicals) must all be extracted and processed. The production of these parts and their assembly in factories produce further emissions that lead to climate change.
Even the roads that cars drive on have an effect. Clearing natural vegetation and covering up ground with the dark surfaces of roads leads to the absorption of heat radiating from the sun. Places with more pavement tend to get hotter on sunny days and stay hotter longer because the paved ground cannot quickly shed the heat it absorbs.