One of the common false arguments contrarians make is that climate change data is not available to anyone but climate scientists and they could prove the scientists wrong if they just had access to the data. This, of course, is false in multiple ways. The first being they are not going to prove climate scientists wrong, no matter how much data they have. The second being, the data is freely available to anyone with a Internet connection.
The National Climatic Data Center (NCDC) has all available climate data online for anyone to access. The National Snow and Ice Data Center (NSIDC) has ice and snow data. And, NASA Goddard Institute for Space Studies (NASA GISS) has satellite data. These are just a sample of the data available. So, anyone that claims they are denied the data clearly has not done their homework.
Now, this amount of data has just been increased. NASA and JAXA have made the data from the Global Precipitation Measurement (GPM) satellite available to the public. This mission is a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA), with contributions from other countries, was launched this past February 27 and measures worldwide precipitation.
If you would like to access the data you can find it here.