What does it mean if the earth's axial tilt is decreasing? How will this decrease affect weather, seasons, etc. on earth?
A decreasing axial tilt means that the tropic of cancer and capricorn are moving closer to the equator and the arctic and antarctic circle are moving closer to the poles.
The earth's axial tilt, which is also know as obliquity, oscillates between about 22.1 degrees and 24.5 degrees with a period of about 41,000 years. It is currently at 23.44 degrees and decreasing.
A decreasing axial tilt means that the topics of cancer and capricorn are moving closer to the equator. This means that the tropical zone is getting smaller. Likewise the arctic and antarctic circles are moving nearer to the poles which means that the polar regions are also shrinking.
At latitudes between the tropical and polar regions, the Summer days will get slightly shorter and the Winter days will get slightly longer. This will lead to slightly cooler Summers and warmer Winters.