An anomaly is the difference between an actual value and some long-term average value.

The standard, or near-average, atmospheric pressure at sea level on the Earth is 1013.25 millibars, or about 14.7 pounds per square inch.

The dew point is the temperature to which the air must be cooled at constant pressure in order for it become saturated, i.e., the relative humidity becomes 100%.

Relative humidity gives the ratio of how much moisture the air is holding to how much moisture it could hold at a given temperature.

Background information on El Niño/Southern Oscillation (ENSO) can be found on the the ENSO Resources page, which provides information on the current forecast status of ENSO conditions and background information on the ENSO phenomenon and some of its associated impacts. There are several other very good websites that have helpful information about El Niño as well.

There are certainly myriad websites that go deeply into the global warming issue.

A relative humidty measurement of 100% does not necessarily mean that rain is falling. It just means that the air is holding as much moisture as it can at a given temperature, in the form of water vapor, which is an invisible gas.

Yes, the phenomenon is known as the lunar atmospheric tide. Although the sun has a greater tidal influence on the atmosphere, the moon does also play a role.

I suggest you start by looking at the Matthews Global Vegetation Index, which shows where the rainforests are, among other things.