What is phenology?
Climatologists use the phenological data observations to assist them while tracking climate data as global warming increases each year. As far as the observational process, this research is not conducted just by the climate change scientists or climatologists or ecologists. Normal, everyday people, otherwise known as citizen scientists, including kids, can also observe, track and record the various phenophases of various plant and animals.
The phenophases are the annual life cycle stages which occur during a plant or animal's life for a year. For example, a common plant phenophase cycle for a deciduous or leaf-bearing tree in the Midwest is when the leaves change color in the fall. Another example is when a plant first emerges or shows initial leaf growth from the ground, followed by the phenophase of breaking leaf buds when just the tip of the new leaf is visible at end of bud. The next phase is when the leaf erupts and fully unfolds as a new leaf but it has not reached it's full size. A flowering plant will display the phenophase which showcases the petals emerging from within the flower bud. The following phases after pollination include the seed set, fruiting and seed dispersal.
Some common animal phenophases are when a robin makes it's first appearance in the spring, when a bear goes into hibernation for the winter, or when various birds or insects migrate.
Many of the plants, animals and even insects all depend on their inner time clocks so that they may all coexist in symbiotic relationships. For example, if a particular plant blooms too early before the insect or migratory pollinators (hummingbirds) have appeared or emerged, the nectar food source for the insect won't be available. The pollinators will not have the food source they need to survive and if the plant doesn't get pollinated, it will not go into to fruiting phenophase which is needed to go into the seeding phenophase.
Sources:
https://www.nwf.org/Wildlife/Wildlife-Conservation/Phenology.aspx
https://www.usanpn.org/about/why-phenology
http://budburst.org/phenology_whyphenology