The costs of achieving emission reductions in the future will depend greatly on the types of policies used to reduce emissions today

Emission reduction policies are the policies which aim at reducing the level of pollution in the environment which is the result of economic activities.

The policies that are implemented today by the government will decide what policies are to be implemented in the future. The reason for this is that the level of emissions which are reduced by the policies implimented today will decide what kind of policies are to be implemented in the future.

If the policies of today are not very effective and do not reduce much emissions level, then stricter policies are to be implemented in the future. But if policies of today are very effective in reducing the level of emissions, then the government doesn't have to impose strict policies in the future.