Citizen science projects involve members of the public helping scientific research by collecting or processing scientific information. With large numbers of people contributing research projects that would be too laborious for a handful of scientists to carry out become possible.
Citizen science projects have great applicability to climate science given the enormous amount of data that can be collected worldwide to inform our understanding of the climate. They are also very useful for gathering historical data. The further back through history we go the more sparse our data on temperature and climate. Much data does exist though in old log books which if digitized can improve our understanding of past climate.
Climate citizen science initiatives include Old Weather (which transcribes ship logbooks to gather otherwise sparse ocean data) and Data Rescue at Home (digitizing various historical weather records from around the globe). So if you have a few spare hours, or want something else to do while watching the cricket, why not help improve our understand of the world?
Ps: If anyone is familiar with other climate citizen science projects, leave a comment.