1. Climate Changes due to Natural Processes
2.6.2a Summarize natural processes that can and have affected global climate (particularly El Niño/La Niña, volcanic eruptions, sunspots, shifts in Earth's orbit, and carbon dioxide fluctuations).

2. Climatic Changes
Climatic Changes
During the average human lifetime, climates do not appear to change significantly.
Climatic change is constantly ongoing and usually takes place over extremely long time periods.

3. Climatic Changes
Ice Ages
Ice ages were periods where the average global temperatures decreased by an estimated 5°C and there was extensive glacial coverage.
Ice ages alternate with warm periods called interglacial intervals.
The most recent ice age ended only about 10,000 years ago.

4. Climatic Changes
Ice Ages

5. Climatic Changes
Change Can Be Natural
Climatic changes occurred long before humans came on the scene.
Studies of tree rings, ice-core samples, fossils, and radiocarbon samples provide evidence of past climatic changes.
These changes in Earth’s climate were caused by natural events such as variations in solar activity, changes in Earth’s tilt and orbit, and volcanic eruptions.

6. Change Can Be Natural Solar Activity
Climatic Changes
Change Can Be Natural
Solar Activity
The existence of sunspot cycles lasting approximately 11 years had been recognized since the days of Galileo.
Studies indicate that increased solar activity coincides with warmer-than-normal climates, while periods of low solar activity coincide with cold climatic conditions.

7. Climatic Changes
Change Can Be Natural
Solar Activity

8. Is the sun causing climate change now?
“In the past four decades at least — we’ve measured the Sun’s brightness since 1978, using very precise space-based instruments”– Lean explains. “And the overall trend has been downwards by a few tenths of a percent.”
Yet at the same time, the global surface temperature has increased by about 1.1⁰F (0.6⁰C). If the Sun’s irradiance were the dominant force driving changes to our climate, the planet should be experiencing a slight cooling.
Source: Judith Lean, Naval Research Laboratory, Washington D.C., October 2015

9. Change Can Be Natural Earth’s Orbit
Climatic Changes
Change Can Be Natural
Earth’s Orbit
Climatic changes may also be triggered by changes in Earth’s axis and orbit.
The shape of Earth’s elliptical orbit appears to change, becoming more elliptical, then more circular, over the course of a 100,000-year cycle.

10. Change Can Be Natural Earth’s Orbit
Climatic Changes
Change Can Be Natural
Earth’s Orbit
When the orbit elongates, Earth passes closer to the Sun, and temperatures become warmer than normal.
When the orbit is more circular, Earth is farther from the Sun and temperatures dip below average.

11. Change Can Be Natural Earth’s Orbit
Climatic Changes
Change Can Be Natural
Earth’s Orbit
The angle of Earth’s tilt varies from a minimum of 22.1° to a maximum of 24.5° every 41,000 years.
Scientists theorize that these changes in angle cause seasons to become more severe and may cause ice ages.

12. Milankovitch Cycles
Natural global warming, and cooling, is considered to be initiated by Milankovitch cycles. These orbital and axial variations influence the initiation of climate change in long-term natural cycles of 'ice ages' and 'warm periods' known as 'glacial' and 'interglacial' periods. Our current climate forcing shows we are outside of that natural cycle forcing range.
Source: Open Source Solutions Systems, Science, Solutions,

13. Natural Cycle of Cooling/Warming

14. What should the climate look like?

15. Change Can Be Natural Volcanic Activity
Climatic Changes
Change Can Be Natural
Volcanic Activity
Climatic changes can also be triggered by the immense quantities of dust released into the atmosphere during major volcanic eruptions.
Volcanic dust can remain suspended in the atmosphere for several years, blocking incoming solar radiation and thus lowering global temperatures.
Some scientists theorize that periods of high volcanic activity cause cool climatic periods.

16. Are volcanoes causing climate change now?
Published estimates based on research findings of the past 30 years for present-day global emission rates of carbon dioxide from subaerial and submarine volcanoes range from about 150 million to 270 million metric tons of carbon dioxide per year, with an average of about 200 million metric tons, These global volcanic estimates are utterly dwarfed by carbon dioxide emissions from fossil fuel burning, cement production, gas flaring and land use changes; these emissions accounted for some 36,300 million metric tons of carbon dioxide in 2008, according to an international study published in the December 2009 issue of Nature Geoscience. Even if you take the highest estimate of volcanic carbon dioxide emissions, at 270 million metric tons per year, human-emitted carbon dioxide levels are more than 130 times higher than volcanic emissions.
Source: Terry Gerlach, from USGS data, 2010

18. How do we know it’s from humans?
The isotopes (C12 v. C13 ) formed from burning fossil fuels can be measured and compared to atmospheric Carbon.

20. Air Quality is connected to climate change too!

21. Conclusions CO2 levels are rising, regardless of the cause.
Impacts on the global ecosystems:
Increase in extreme weather, floods, droughts, extreme hurricanes, etc.
Spread of diseases due to increased range of tolerance by various species
Species loss, Ocean acidification
Issues with farming (crop failures)
Sea level rise