CH4+2O2 gives CO2+2H20, so it humidifies air.
Now convectional rain can be brought about merely by having a piece of darker ground heating up more than surrounding lighter coloured ground (urban heat island effect and so on).
If you have 100 tonnes of trees per hectare (100 m by 100 m) then this can create 170 tonnes of carbon dioxide if burned. If one could create rain with a tonne of natural gas over a hectare, it would create 2.75 tonnes of carbon dioxide, but save 170 tonnes of carbon dioxide from being spewed into the air by fire. The natural gas industry could theoretically prevent greenhouse gas emission from forest fires dramatically.
Gas companies could use the following method in deserts to get trees to grow: Use a bulldozer to bulldoze any rocks in the area to a specific location. The rocks will heat up during the day and retain some of their heat during the night.. At night when relative humidity increases, use a gas grid in the rocky area to humidify the air more and cause more convection. The rocks could be dyed a dark colour so they get hotter in the sun (a fairly natural dye such as a dark metal oxide could be used).The amount of water vapour produced by one tonne of gas is about 2.25 tonnes. Because relative humidity is already high at night, this will enhance the chances of rain. For instance Cairo often has a temperature of about 26 deg C at night and an RH of 80% at the same time. A parcel of this air, 100 m by 100 m, by 100 m holds 19.5 tonnes of water vapour. If you add 2.25 tonnes to this from the burning gas grid, you increase the water vapour content significantly.