GC 170 1st Edition Exam 4 Study Guide Lectures 14 17 Lecture 14 climate variability and climate change natural forcings What is the difference between Global Warming and Climate Change Climate change Significant change in measures of climate temp precipitation that lasts for an extended period of time Global warming Average increase in temperature in the atmosphere It is only a PART of climate change a big one o Climate change that is related to human activities fossil fuel emissions What is the difference between Climate Change and Climate variability Climate Change Long term changes in the regional climate or earth s average temperature occurring over decades to centuries Climate variability Short term changes in the climate occurring over years to decades usually related to natural climate forcings influences What is a paleoclimate reconstruction Paleoclimate reconstructions thousands of years are developed from proxy records tree rings ice cores pollen records o Key to future understanding past o Historical information provides a context for recent warming o Help us to predict the future environmental conditions Why is it important to study paleoclimate Key to future understanding past Historical information provides a context for recent warming Help us to predict the future environmental conditions What is significant about 20 th century warming compared with the past 2 000 years Major warming over the past few decades o 20th century warming is unpredictable What is the Medieval Warm Period and what is the evidence from this time Medieval warm period o A period from 900 1300 AD o When average temperature in the northern Hemisphere was warmer 0 5 degrees than the 20th century o Evidence from Northern Europe Vikings in Europe settled in Greenland for 400 years o Medieval Period in Europe was a time of growth many castles were built during the MWP What happened in the southwestern US during the Medieval Warm Period Western US o Arid and warmer across the western US o Several long and severe droughts lasting around 20 years in the Southwest o Large communities of Native Americans dispersed Hard to sustain large communities What is the evidence of the Little Ice Age Cool period from 1400 1800 AD Glaciers more advanced in some places than they are today Holland had a lot of continuous Ice Periods of cooler temperatures glacial advances and more freezing temperatures Natural Climate Forcings What is the climate effect of a large explosive volcanic eruption Volcanic eruptions inject large amounts of ash into atmosphere o Blocks amount of incoming solar radiation reaching the earth surface and cools the climate Explosive volcanic eruptions emit black ash SO2 gas reaches the stratosphere SO2 converts to sulfate aerosols Fine particles that reflect incoming solar radiation remain in the stratosphere for 1 2 years stratosphere is dry sulfate aerosols are not rained out o Cool the global climate for 1 2 years o Volcanoes near equator cool more effectively Upper level winds transport volcanic gases and ash to cover both hemispheres Higher latitudes winds transport the ash and gases to cover a smaller area ex only within the northern hemisphere How do volcanoes cool the climate o Blocks amount of incoming solar radiation reaching the earth surface and cools the climate Explosive volcanic eruptions emit black ash SO2 gas reaches the stratosphere SO2 converts to sulfate aerosols Fine particles that reflect incoming solar radiation remain in the stratosphere for 1 2 years stratosphere is dry sulfate aerosols are not rained out How long is the climate cooled following a volcanic eruption 1 2 years Why are volcanoes near the equator the most effective at cooling the climate globally o Volcanoes near equator cool more effectively Upper level winds transport volcanic gases and ash to cover both hemispheres Higher latitudes winds transport the ash and gases to cover a smaller area ex only within the northern hemisphere How do sunspots affect climate specifically how is the energy budget affected In terms of the energy budget o More solar radiation is absorbed at the earth surface o Earth s surface temperature increases How long does the climate effect last 10 years Did sunspot activity contribute to the cooler period of the Little Ice Age The combination of volcanoes and decreased sunspot activity may be partly responsible for cooler climates during Little Ice Age Does sunspot activity contribute to recent warming of the past few decades Partially because there are natural forcing volcanoes and sun spots but also human forcing use of fossil fuels etc According to the Global Climate Models would there be warming without human influences on climate Yes Lecture 15 Proxy methods ice cores tree rings What is proxy data a Data that represents past environments and climates levels of CO 2 i Before 1958 Keeling Project 1 Found levels of CO2 in ice cores 2 Contain old layers of ice with air bubbles containing CO2 levels in past ii Used to develop paleoclimate reconstructions 1 Key to the future is understanding the past 2 Historical information provides context for recent warming 3 Help predict future environmental conditions What are some examples of natural archives which contain proxy data i ii iii Tree rings Ice cores Pollen records How are ice cores are collected and what happens in the lab to measure the proxy data In the lab o Ice is cut into sections 10 cm 1 m o Ice is melted o Gas bubbles are released o Water is collected Scientists measure o Gas Samples of the atmosphere reconstruct past greenhouse gas concentrations CO2 Methane Nitrous Oxide o Water Temperature Hydrogen isotopes o Dust and Particulates in the ice Dust ash from past volcanic eruptions and pollution Shows repetitive cycles or fluctuations in CO2 Shows unprecedented CO2 levels in recent decades What proxy information can be obtained from ice cores Dust and Particulates in the ice o Dust ash from past volcanic eruptions and pollution Shows repetitive cycles or fluctuations in CO2 Shows unprecedented CO2 levels in recent decades What modern measurements do scientists make in order to have a modern analog for an ice core In order to interpret the past conditions scientists need to understand how ice accumulates and what air bubbles represent Scientists take samples of the modern atmosphere and ice accumulation near the location of the ice core In some places monitoring of CO2 levels and ice accumulation for 40 years What information