(The Ross Ice Shelf, at the Bay of Whales, is the southern-most navigable point on Earth. Credit: Michael Van Woert, National Oceanic and Atmospheric Association (NOAA) NESDIS, ORA)

One of the most convincing things about climate change research is that it involves observations and knowledge from a wide variety of scientific disciplines, and where the historical data from each can be compared, it matches up well.

Scientists have long looked to historical records to make predictions for the future. Edmund Halley used what he knew of past appearances of comets to predict the return of the comet which now bears his name. As well as appearing in the Bayeux Tapestry celebrating 1066, it was recorded by Chinese astronomers on 30 March 239 BC. Today there is still a role for amateur astronomers, who have discovered Uranus, comets, galaxies, supernovae and other objects and anomalies that excited the professionals.

Scientists and diarists have been recording what they see, hear, and otherwise sense for millennia. Even when they did not have writing, they have been known to pass down memories for more than 7,000 years, as Australian aboriginals did for changes in their coastline.

People have recorded the weather, the signs of the changing of the seasons, the temperature, ice extent and many other items of information useful to climate scientists. Sometimes this has to be calibrated very carefully before it can be compared with readings from modern scientific instruments. Temperature measurements that were taken in the countryside have to be adjusted before they can be compared with measurements taken in the same place now, to allow for urban heat island effect, if a city has grown up there in the meantime. Thermometers have changed, too. We now have standards for local weather stations - the thermometers must be of a certain type and quality and the station must be a standard height from the ground and a certain distance from items which might affect the wind speed, etc. The UK Met Office and Weather Underground have personal weather station networks you can join.

Many of the observations were written down in diaries, and therefore not easy for climate scientists to access. It is important to have as many records available as possible, to fill in gaps in our knowledge, to tell if trends are long or short term, to test the climate models to see how well they predict the observations (which increases confidence in predictions for the future), and to provide a firm starting point for model runs.

One new project led by NOAA, Old Weather: Whaling, is looking for volunteers to search for new clues about climate history from online reproductions of old whaling logbooks, in which whalers recorded a lot of information about weather and sea ice extent on their travels. Find out more about it here. The same team also runs Old Weather, using logs from other U.S. ships. Both projects are part of Zooniverse - people-powered research in fields ranging from astronomy to zoology.

While there is no substitute for on the spot observations, they are in nature very spotty. These days we have a variety of satellites to provide information on one or more aspects of climate for most or all of the planet, and these satellite observations can be compared with measurements on the ground, for calibration and to increase our confidence in them and our understanding of what the satellites are telling us. Europe's Cryosat radar spacecraft are now giving us more detail than ever about the height of sea ice around the world. For example, it shows that Greenland is losing ice to the ocean. But historical data from fishing vessels is needed to give some idea how unusual this is.

As an alternative to direct observation and measurement, a variety of climate proxies are used, as Dr. Michael Mann explained recently on The Big Picture:

And so what we did back in the late 1990s was use information from what we call proxy records. These are indirect thermometers. They're things like tree rings and corals and ice cores and sediments, various physical or chemical measurements from our environment that actually tell us something about past climate conditions. And we use those data to reconstruct how the temperature of the northern hemisphere had changed over the past thousand years.

Citizen Scientists can also get involved with some of these. For example, Queen Mary College London has a project called OMEGA–LOCATE to study nonmarine ostracods, tiny crustaceans with an excellent fossil record which are common in aquatic ecosystems.

Scientists have also involved citizen scientists' computers in a number of distributed computing projects where people give time on their computers for a variety of areas of research such as SETI@home which is engaged in the Search for Extraterrestrial Intelligence, Help Conquer Cancer, and Climateprediction.net, which runs climate models on people’s home computers to help answer questions about how climate change is affecting our world, now and in the future.

So, simply decide what kind of research interests you (e.g. climate, health), how much money (if any) you want to spend, and how much time you and/or your computer can spare, and follow one or more of the above links or search the Internet to find a project to suit (this article has mentioned only a small sample).

You, too, can join the ranks of amateur scientists like Sir Isaac Newton, Benjamin Franklin, and Charles Darwin. Good hunting!