The "second screening" is possible in MeteoEarth from the iPhone 4S, iPod 4G and iPad 3 onwards.
Both your iOS device and Apple TV must be on the same wireless network. In addition, please make sure that you have enabled Apple TV in the MeteoEarth settings.
Open the Control Panel by swiping from the bottom to the top of the screen, thus pulling the lower taskbar. Tap AirPlay and then click the name of the Apple TV that you want to add to AirPlay. Then activate the "screen sync."
Even with an iPad 2 there are functions to connect to the Apple TV, but not as a "second screening," just as a one-to-one copy. For this the setting "Apple TV" in the MeteoEarth settings must not be enabled.