First, the carbon dioxide added to the Earth system by human activities is indeed small in comparison to the amount of CO2 that moves naturally between atmosphere, ocean, and land. However, the added carbon tips the natural balance, and is the dominant cause of the change that has been observed in the Earth’s climate, in sea-ice area, in sea level, in ocean acidification, and in many other systems.
Second, the effect of “planetary, lunar, solar, and celestial” processes on climate change are inconsequential in comparison to the scale of present human activities. For example, we currently emit more than 24 times the CO2 (equivalent) emitted by volcanoes and natural geological processes on an annual average.
Natural processes mentioned in Lane’s letter do not explain the observations. Humans are the cause of observed climate and related changes. Human activities include carbon added to the atmosphere, as CO2 and methane (natural gas) from fossil-sourced fuels, CO2 from the production of cement, land-use change, and more. This is accepted by scientists and lay-people everywhere. It’s the position of every national science organization on Earth. It’s a fact.
For references and more information start with the IPCC summary documents. Or, use resources from the many credible government, national, and university-based organizations around the world. Send me an email (firstname.lastname@example.org), I can point you in the right direction.
It’s time to stop the pretend debate and to take seriously the need to act to reduce future harm.