My impression is that this “3%” generally consists of scientists who acknowledge that CO₂ is rising due to human activities, and who also acknowledge that this rising CO₂ will cause some global warming, but who disagree on the amount of warming it will cause.

We believe that the fundamental trigger for the end of the last ice age was increasing insolation (more heating from the sun) over the northern hemisphere, where the main glacial ice cap sat.

Ozone is an atmospheric gas made of three oxygen atoms bound together (chemical formula O₃). It constitutes a very small fraction of the air close to the Earth’s surface which we breathe in and out every day.

Natural fluctuations are indeed a feature of Earth’s climate. But, if we look at the climate of the past 150 years (for which we have direct temperature measurements) and compare to climate models, we find that the observed warming of the past 30 years or so is outside the range of natural fluctuations produced by models.

Science has advanced to the point where we can analyze an extreme event and tease out the role that climate change played in that event—how much more/less likely, how much stronger/weaker.

The last time the atmospheric CO₂ was above 1000 ppm was probably the Triassic, more than 200 million years ago. Atmospheric CO₂ has varied in the past. It was as high as 4000 ppm in the Cambrian (500 million years ago), before vertebrates evolved. This was a period of arthropods like Trilobites.

The short answer? No. But that doesn’t mean there is no need for worry.

There are two important ways the ocean controls climate: through the heat that the ocean holds and the gas exchange with the atmosphere. The ocean (and water in general) has a higher heat capacity than air or land.