claim: So that means that probably about half, maybe half of that nine-tenths of the degree [of total warming] might be caused by greenhouse gases
evidence: Multiple factors—some human-caused and some natural—combine to influence global temperatures. However, human activities were already causing warming in the first half of the 20th century, and are responsible for approximately 100% of the more-rapid warming taking place after 1950. Thus, humans are responsible for most of the warming since 1900.