OK, what's "phenology."
Phenology is the science dealing with relationships between climate and periodic biological phenomena.
Well, you know what climate is and if you think about it you also know what "periodic biological phenomena" are. They are events such as:
You see, everything is a when and everything is something in nature that repeats itself at a certain time during the year's annual cycle. You could probably sit down now and make a list of a hundred or more such activities right off the top of your head.
Many backyard naturalists keep phenological records simply because it's fun to do. It's fun to pay attention to such things as are mentioned above, and it's fun to compare this year's records with last year's, and of years before.
In fact, when you keep good phenological records for many years, they can actually become very important documents, not only for yourself but also for science. That's because nowadays one of the biggest and most worrisome questions in all of natural science is, Is air pollution causing the Earth to warm up? Is "global warming" about to cause a disastrous change in the Earth's ecosystem?
NORTH AMERICAN STUDENTS:
Phenology on The Web
K-12 students can share their own field observations with classmates across North America at the Journey North website. Migration patterns of monarch butterflies, robins, hummingbirds, whooping cranes, gray whales, bald eagles, other birds and mammals, the budding of plants, changing sunlight and much more is taken note of. The site offers migration maps, pictures, standards-based lesson plans, activities and information to help students make local observations and fit them into a global context.
If you'd like to participate in real research, take a look at the USA National Phenology Network website.
Some of the most important data being used nowadays to answer this question is that of phenological records. If it can be shown, for instance, that years ago the first catkins produced on Black Oak trees were on or around May 1, but nowadays they usually appear by April 15, then that is a strong hint that global warming is taking place. If phenological records show that the same early-flowering tendency is being observed among nearly all species in many locations all over the Earth, then that is very strong proof indeed. Unfortunately, we just don't have enough phenological records from many places to answer this simple question.
Science needs good phenological records!
You can decide for yourself how to keep such records in your own Nature Notebook. The important thing is have a clear idea of that exact moment when a flower can be considered "blossomed," and when migration of a certain bird species has begun. You must know the basic life-cycle facts about the thing you're observing, and you must observe your organism very closely and frequently.