Vulnerability to long-term climate cycles

Vulnerability to long-term variations in solar radiant energy

Nature

Climate changes during the course of long-term cycles which appear to reflect an astronomical forcing of the climatic system by changes in the seasonal patterns of insulation. These are driven by changes in the orbital parameters of the Earth, specifically due to variations in the tilt of the rotation of the axis and due to secular precession of the rotation axis. A complete precessional cycle is described every 26,000 years, and with the slow rotation of the orbit effectively changes the position of the Earth relative to the sun for any particular season. These changes in insulation play a critical role in determining whether ice sheets advance or retreat, as well as affecting the biological productivity of the oceans and the level of carbon dioxide in the atmosphere.

Background

The significance of vulnerability to long-term climate cycles emerged in the early 20th century, as scientists correlated historical famines, droughts, and societal collapses with recurring climatic patterns such as the El Niño-Southern Oscillation and the Atlantic Multidecadal Oscillation. Subsequent advances in paleoclimatology and global data collection revealed the pervasive influence of these cycles on agriculture, water resources, and human settlement, prompting international research into adaptive strategies and risk assessment.

Incidence

Major changes in climate occur approximately every 100,000 years, with associated changes of sea level of approximately 100 metres. Other changes occur in cycles of 41,000 years and 23,000 years, with subsidiary changes occurring in cycles of 59,000 years and 11,000 years. Changes in insulation of lesser significance are also expected, at 100,000 and 413,000 years due to changes in the ellipticity of the Earth's orbit. At present the Earth is relatively close to the sun during the northern winter, but the opposite situation will prevail in 11,000 years.

The great climatic changes of the past 2 million years created stress among living things. Forest, grassland and animal populations were repeatedly forced to change and migrate as glaciers waxed and waned. The most significant changes occurred in the sub-tropical deserts of the northern hemisphere. The Sahara was wetter (rock paintings there depict hunters of big game in extensive Savannah grasslands). The Indus Valley civilization of Mohenjo-Daro and Harappa arose during this wetter period, but subsequently faded because of climatic change. In the past 4000 years, this desiccation has predominated in much of the sub-tropical belt.

Claim

Vulnerability to long-term climate cycles is an urgent and critical problem that cannot be ignored. These cycles threaten food security, water resources, and entire ecosystems, putting millions of lives and livelihoods at risk. Failing to address this vulnerability is reckless and short-sighted, as it undermines our ability to adapt and survive in a rapidly changing world. Immediate, decisive action is essential to safeguard our future against the devastating impacts of climate variability.

Counter-claim

Concerns about vulnerability to long-term climate cycles are vastly overstated. Natural climate fluctuations have occurred for millennia, and humanity has always adapted. Focusing on these distant, slow-moving cycles distracts from immediate, tangible issues that actually impact daily life. Resources and attention should be directed toward real, pressing problems—not hypothetical scenarios that may or may not unfold over centuries. Worrying about long-term climate cycles is simply not an important problem.