Here are useful links to climate related data sources
NASA Earth Observatory and NOAA
NASA Cloud Product: Description of the tool.
AIRS data: Various data of the atmosphere
NOAA: Global Historical Climatology Network (GHCN)
Arctic and Antarctic interactive sea ice graph
Artic Sea Ice Extend for Arctic and Antarctic
Temperature.global: Online measurement and overview of global temperature
DWD (Deutscher Wetterdienst): Historical Temperature measurements in Germany (1781 until present)
Climate4you: A collection of many different climate relevant data.
Creating plots from various sources: WoodForTrees
KNMI Climate Explorer (initialized for maximum Temperatures in Siberia)
MODTRAN Interactive Tool for OLR IR spectra and Downwelling IR spectra
HITRAN etc: Spectroscopic Data base.
Agora – Statistics of the German energy transition
Agora-Energiewende: Useful information of hourly current energy mix in Germany including corresponding electricity trading prices.