Due to the rapid growth of Cloud services, data centers have become major energy consumers, resulting in significant CO2 emissions. Several infrastructure-focused strategies,such as resource consolidation, have been used to reduce the carbon footprint of Cloud infrastructure. However, end-users are often left out of the picture. Since they are the primary target of Cloud applications, it would be beneficial to actively involve them in reducing the carbon footprint of Cloud applications. In this paper, we offer end-users a way to influence the carbon footprint of cloud applications they use. To this end, we ask end-users to select a high-level mode to control the carbon footprint of a cloud application. We then design a dynamic adaptation algorithm that determines an appropriate configuration for the application for each request, based on the end-user mode and on the carbon intensity of the infrastructure energy sources. We implement and evaluate our system on a simple image-resizing application. We run experiments on SeDuCe, a Cloud infrastructure testbed partially powered by solar panels. Our results show that we save energy consumption by up to 84% when all end-users agree to degrade the quality of the application’s output, and we provide a good quality-energy trade-off when end-users make heterogeneous choices. In addition, we are able to improve quality by leveraging the available green energy budget.