The theory of Earth's climate in the last 15 million years is based on a large body of evidence from a variety of sources, including ice core data, sediment records, and fossil evidence. This evidence indicates that the Earth's climate has undergone significant changes during this time period, including several periods of global warming and cooling. The theory of Earth's climate in the last 15 million years is supported by the majority of scientists, and there is no evidence to suggest that it is wrong.

However, there is some debate about the details of the theory, such as the exact timing and magnitude of the different periods of global warming and cooling. This is because the evidence is not always complete or unambiguous, and there are different ways to interpret the data. As a result, there are some scientists who have proposed alternative theories about the Earth's climate in the last 15 million years.

One alternative theory is that the Earth's climate has been relatively stable for the last 15 million years, with only minor fluctuations in temperature. This theory is based on the evidence that the Earth's temperature has remained relatively constant for the last 10,000 years, and that the Earth's climate has not undergone any major changes during this time.

Another alternative theory is that the Earth's climate is controlled by a combination of factors, including solar radiation, volcanic activity, and changes in the Earth's orbit. This theory is based on the evidence that the Earth's climate has changed in response to changes in these factors in the past.

The debate about the theory of Earth's climate in the last 15 million years is likely to continue for some time. However, the majority of scientists believe that the theory is essentially correct, and that the Earth's climate has undergone significant changes during this time period.