Vidqun:
"By the way, other planets of our solar system are also heating up, e.g. Jupiter. Might the problem not lie with the sun, earth's distance from the sun and the tilt of the earth?"
@Vidqun,I looked this up because I noticed you have posted this before. There are a couple of problems with this idea. For one, the Sun has been radiating less heat over over the last 50 years.
Any proof of heating on other bodies in the solar system is non-existant, it has only only been conjectured because of visual observations, not actual temperature measurements.
Jupiter receives about 4% of the radiation the earth receives from the Sun because of its distance from the earth, it actually generates more heat internally than it receives from the Sun.
As far as the angle of axis goes, why would it matter? All planets have elliptical orbits and therefore the distance they are from the Sun varies throughout their year. Not all planets have a nice 23.5 degree tilt like the earth. Uranus's angle of axis is 97 degrees.
In the case of Neptune, its 'year' is 164 earth years, so any claims that its climate is changing, or getting hotter would have to be observed over a much longer period than a few years to get an accurate picture.
In short, it sounds like the sort of claims people would make trying to normalise global warming right here on Earth.