The glacial cycle averages about 100,000 years, consisting of about 90,000 years of the glacial period, when mile-thick continental glaciers blanketed much of the Northern and Southern Hemispheres including Canada, Russia, Northern Europe and Northern USA, and about 10,000 years of interglacial, the warm period of the present.

Earth is now 11,500 years into the current warm interglacial, and our planet may re-enter the glacial period at any time.

Geoengineering

Geoengineering is any large-scale interference in the climate system to counteract global warming. In some interpretations of this definition, concepts such as CCS and biochar, and even large-scale afforestation projects, can be included. However, more commonly, geoengineering is used to encompass some of the less conventional ideas for combating global warming. Under this view, geoengineering concepts fit into two categories:

carbon dioxide reduction techniques aim to reduce existing concentrations of atmospheric carbon. Examples include:
chemically ‘extracting’ CO2 out of the air with tree-mimicking devices, and
adding iron to the ocean to stimulate biological growth that absorbs CO2 from the air and eventually sinks to the seabed.
solar radiation management aims to either reduce the amount of incoming solar radiation, or increase the amount reflected. Some proposed methods are:
whitening clouds with tiny salt water droplets to make them more reflective
engineering whiter crops or covering deserts with reflective material
injecting sulphur dioxide into the stratosphere to reflect sunlight, and
propelling mirrors into space to reflect incoming radiation.

These ideas are untested, and could have dangerous side-effects.

Some geoengineering methods could reduce average rainfall globally, delay the recovery of the ozone hole by up to 70 years, suffocate marine ecosystems, or even cause failure of the Asian and African monsoons thus threatening the lives of millions.
The very concept of geoengineering also poses a series of complex ethical and legal questions around the issues of global management and treatment of global commons. And who is to blame if or when the side effects prove disastrous?

Although these questions seem premature, they must be considered throughout any discussions and be integral to the direction of any research. It is likely that global politics, not science, will be the major hurdle for geoengineering.

https://www.aph.gov.au/About_Parliament/Parliamentary_Departments/Parliamentary_...

It's 2029 and every merchant ship in the world is fertilising the ocean with iron — a last-ditch effort to draw carbon dioxide from the air as global emissions near the point of no return.

This global attempt to remove CO2 from the atmosphere has been 11 years in the making — since 2018, when the IPCC Global Warming of 1.5C special report warned that emissions reductions alone would not be enough to restrict global heating to 1.5 degrees Celsius.

Removing carbon dioxide from the atmosphere would also be required.

The hope is that the powdered iron will trigger a bloom of phytoplankton that will remove a gigatonne of CO2 from the atmosphere, by taking the carbon to the ocean floor when they die.

https://www.abc.net.au/news/science/2019-10-07/scientists-warn-we-have-10-years-...