As I described in an earlier post, providing evidence of psychokinetic abilities is rather simple (well, for aerokinesis, atmokinesis, and in some ways, probably geokinesis)
Can you control the weather? Can you control the wind? The earth?
If you can, post what you want the weather to do (being exact, stating exact miles an hour if it is just wind, and exact wind speeds and weather conditions if it is atmokinesis). Try doing this on days that have meteorological predictions, trying to make them the opposite of what was predicted. Post both your aerokinetic/atmokinetic desires on here along with a TIME-STAMPED JPEG or link to the REPUTABLE weather site (like weather.com) so others can see and compare your results with the original predictions. I would strongly suggest making a JPEG, because websites update a lot, especially weather sites, and so a JPEG would capture the predictions in time, and they wouldn't change.
For geokinetics, if you claim to, and are actually able to, cause tremors or earthquakes, simply post on here, when, where and how strong your tremor will be (and by how strong, I mean where it would fall on the Richter scale... like 3.5, 4.8, 7.9, etc.).
This method would work, I believe,for the simple fact that your "before-the-fact" predictions would be seen and noted here, you would have data to compare it to (for the aero/atmokinetics, you would use the weather sites, and for the geokinetics, you would just simply copy and paste the story from the area you were talking about saying that there was an earthquake with the magnitude you were aiming for on the date you were aiming for)
This method is perfect for those who say they don't have cameras; you don't need one, and if you are chatting on his forum, you obviously have a computer and the internet, an these are the only things you would need. That simple