This year, nearly 200 nations convened in Paris to discuss the future of the planet. The issue at hand was climate change. With greenhouse gases pumped into the air by various forms of industry, the temperature of the Earth is rising, slowly but surely. The last five years are the hottest five-year span ever recorded, and this year the average temperature of the Earth is expected to reach 1 degree Celsius above pre-industrial levels.

COP21 set both a promise and a goal, signed off on by every country in attendance. The promise is to limit global warming to 2 degrees Celsius above pre-industrial levels by 2100. The goal is 1.5 degrees. Under current policies, the Earth’s temperature is predicted to reach 3.6 degrees above those levels by 2100, and even the new policies established at COP21 would only limit warming to 2.7 degrees.

It’s clear that to meet this goal, countries around the world will have to make drastic changes in climate policies, and those changes must come as soon as possible. With transportation currently responsible for 27 percent of greenhouse gas emissions, the auto industry is likely to be the target of several new policies.

Emissions

The most direct way of reducing greenhouse gas is to place stricter emissions regulations on gas and diesel vehicles. These regulations are effectively a compromise. Reducing emissions usually comes at the cost of some amount of power and efficiency, so we may see a slightly decline in these across the board if tighter regulations are established.

While it would cost a not-insignificant amount of money, most car companies could reduce emissions without any radical design changes. Methods of controlling greenhouse gases are well-established, but emissions are not usually a customer priority, whereas power and efficiency often are. That means manufacturers also deprioritize limiting emissions. Taken to the extreme, this explains the recent Volkswagen scandal, where the company installed software that enable cars to cheat emissions tests in order to keep the additional performance that comes with disabling devices that control greenhouse gases.

Reducing emissions essentially boils down to making sure as much of the fuel as possible has combusted before the remaining molecules are expelled through the exhaust system. The ideal way to do this is by ensuring more efficient combustion in the cylinder, which also increases performance and fuel efficiency. Unfortunately, most manufacturers have explored this option to the extent that there is little headway to be made. Some radical cylinder head designs, however, could in theory slightly increase combustion efficiency.

Another way emissions can be reduced is by injecting exhaust gases back into the cylinder to give remaining hydrocarbons another chance to be broken up. This must process must be carefully controlled by computer, however. If too much oxygen is displaced by exhaust gases, combustion will not occur.

One of the more promising areas for improvement is the catalytic converter. This is the last line of defense for greenhouse gases, breaking down hydrocarbons through a passive chemical process. Catalytic converters are not 100 percent effective, and the design has remained largely unchanged for some time. Dedicated computer simulations could discover a more effective layout than the standard honeycomb pattern, although such a design would likely be more difficult to manufacture.

Catalytic converters also don’t operate well when cold. Some cars use electric heaters to bring the converter up to operating temperature quickly, which can significantly reduce emissions during the first few minutes of operation after a cold start. Adding this system to all cars would be an easy way to reduce overall emissions.

Fuel Efficiency

Unlike emissions, fuel efficiency has been a priority in the car industry for some time. The spike in gas prices a few years ago caused many customers to place fuel efficiency among their highest considerations when buying a new car, and the industry has responded to that demand. Even among performance cars, manufacturers are finding ways to squeeze out a few extra mpg. For example, the Ford Mustang’s new EcoBoost engine manages to put out more than 300 horsepower and more than 30 mpg, thanks to a creative turbocharged I-4 design.

Government requirements for fuel efficiency have already been a huge motivating factor for the industry, and the highest requirements will be rolled out in 2016, where manufacturers will be expected to meet an average of 37.8 mpg for cars and 28.8 mpg for trucks. Vehicles that go above and beyond these requirements provide credit that allows for less efficient ones, such as performance cars. Ford’s various sedans will have to significantly exceed that mark to accommodate the Mustang GT’s less efficient V8 engine.

Hybrid and Electric Vehicles

Many car manufacturers are already producing plug-in hybrid and electric vehicles. These cars can run without using gas at all, preventing the release of greenhouse gases into the atmosphere. These efforts will likely be expanded in the future, especially if further overall fuel-efficiency requirements are put in place after 2016.

Another factor that could spur increased demand for electric cars is a carbon tax or cap-and-trade system like the one China recently put in place. The U.S. doesn’t currently tax carbon emissions, but with even oil companies like ExxonMobil recommending some form of carbon tax, that may change in the near future. Such a tax would slightly raise gas prices, but could also tax consumers directly for carbon emissions from their vehicles, creating additional incentive to look at alternative fuel options.

Without any new policies directly affecting the auto industry, it’s difficult to predict exactly how the commitment to climate change reform at COP21 will affect car manufacturers. However, past changes in environmental regulations can provide some picture of what might be to come. If the countries involved are serious about honoring this commitment, expect stricter emissions and fuel-efficiency requirements to come in 2016 and beyond.