There is no universally accepted system for classifying "six major climate groups." The most common way to categorize climates is based on the Köppen climate classification system, which uses five major climate groups, each with several subcategories.

The five major Köppen climate groups are:

1. A: Tropical Climates: Hot and humid year-round.

2. B: Dry Climates: Characterized by low precipitation.

3. C: Temperate Climates: Moderate temperatures with distinct seasons.

4. D: Continental Climates: Cold winters and warm summers.

5. E: Polar Climates: Very cold temperatures throughout the year.

These categories are further divided into subcategories based on specific temperature and precipitation characteristics.

Other climate classification systems exist, but the Köppen system remains the most widely used.

It's important to note that climate classification is a complex process and there's no single "best" system. Different systems emphasize different aspects of climate and have their own strengths and weaknesses.