L3 - Natural variability of climate Flashcards
What is the focus of the IPCC special report?
The impacts of global warming of 1.5°C above pre-industrial levels, related greenhouse gas (GHG) emission pathways, and strategies to strengthen the global response to climate change while promoting sustainable development and poverty eradication.
How has global average temperature varied over the last million years?
It has followed a cyclic pattern, with peaks of extreme warming followed by troughs of extreme cooling every 100,000 years.
When was the most recent ice age, and how much cooler was it than today?
It occurred 20,000 years ago, with global temperatures about 5°C cooler than today.
What were the sea levels like during the last ice age?
Sea levels were 120 meters lower than today.
What are the main drivers of natural climate variability?
Orbital variations (Milankovitch cycles)
Solar variability (changes in the Sun’s energy output)
Volcanic activity (aerosols and sulfur dioxide causing temporary cooling)
Ocean circulation (e.g., El Niño and La Niña influencing global climate patterns)
What are Milankovitch cycles?
They describe changes in Earth’s orbit and axial tilt that affect the distribution and intensity of solar radiation received by Earth, driving long-term climate variability
What are the three main components of Milankovitch cycles?
Eccentricity – Changes in the shape of Earth’s orbit (100,000-year cycle)
Obliquity – Changes in the tilt of Earth’s axis (41,000-year cycle)
Precession – Wobbling of Earth’s axis (26,000-year cycle)
What is eccentricity?
It describes how Earth’s orbit changes from more circular to more elliptical over tens to hundreds of thousands of years.
How does high eccentricity affect climate?
It increases the difference in solar radiation received during different seasons, affecting global temperatures
What is Earth’s current orbital eccentricity?
0.0167 (nearly circular), causing a 3.3% difference in Earth-Sun distance between June and December.
How does obliquity affect climate?
Greater tilt (up to 24.5°) = Stronger seasonal contrasts
Lesser tilt (down to 22.1°) = Weaker seasonal contrasts
Currently, Earth’s axial tilt is 23.5°
What is precession?
A gradual wobbling of Earth’s axis over a 26,000-year cycle that shifts the timing of seasons and alters solar radiation distribution.
How does precession impact climate?
It changes which hemisphere experiences summer when Earth is closest to the Sun, influencing seasonal temperature differences.
How does solar activity affect Earth’s climate?
Changes in solar output influence the amount of solar energy reaching Earth, affecting temperature patterns.
What is the 11-year solar cycle?
A periodic increase and decrease in sunspots, with peak activity increasing the Sun’s brightness by 0.1%.
What was the Maunder Minimum?
A period from 1645 to 1715 when sunspots were nearly absent, contributing to the “Little Ice Age.”
How do volcanic eruptions affect climate?
They inject sulfur dioxide and aerosols into the stratosphere, reflecting sunlight and causing temporary cooling.
What was the impact of the 1991 Mt. Pinatubo eruption?
It released 20 million tons of sulfur dioxide, cooling global temperatures by several tenths of a degree
What is ENSO?
The El Niño-Southern Oscillation, a large-scale fluctuation in ocean temperatures and atmospheric pressure that affects global climate.
What happens during El Niño?
Weakens Walker Circulation
Warmer sea surface temperatures in the eastern Pacific
Reduces upwelling of cold water
Warms global temperatures
What happens during La Niña?
Strengthens Walker Circulation
Cooler sea surface temperatures in the eastern Pacific
Increased upwelling of cold, nutrient-rich water
Cools global temperatures
How is ENSO monitored?
By measuring air pressure differences (SOI), sea surface temperatures, and wind patterns across the Pacific.
How does ENSO impact global temperatures?
El Niño warms global temperatures with a lag as heat redistributes.
La Niña cools global temperatures with a similar delay.
what is walker circulation
Normally the equatorial pacific ocean has a pool of relatively warm water in the upper ocean in the west and a shallower layer of relatively cool water in the east – maintained by and in balance with easterly surface winds
The well-mixed upper ocean layer lies above a thin thermocline layer, with cold water below
