Final answer:
The phosphorus cycle is least likely to be affected by global warming as it does not contain a significant gas phase and is less influenced by atmospheric changes compared to the carbon, water, and nitrogen cycles.
Step-by-step explanation:
The geochemical cycle that is least likely to be affected by global warming is the phosphorus cycle. Unlike the carbon, nitrogen, and water cycles, the phosphorus cycle does not involve a significant gas phase and is primarily concerned with the movement of phosphorus through the soil, water, and living organisms. As a result, it is less directly influenced by the changes in temperature and atmospheric conditions associated with global warming. The carbon cycle, on the other hand, is highly susceptible to global warming impacts due to its direct involvement with greenhouse gases like carbon dioxide (CO₂). Similarly, the water cycle and nitrogen cycle can also be significantly affected by global warming, influencing their respective atmospheric and biological processes.