global change

For an ice core, what do the scientists measure for each layer?

1) Gas 2) Water 3) Particulates in the ice

What proxy information can be obtained from ice cores?

1) Ice Water = Temperature (Hydrogen isotopes) 2) Gas bubbles used to reconstruct greenhouse Gas concentrations ex:Carbon Dioxide, Methane, Nitrous Oxide 3) Particulates (dust, aerosols) can provide other information ex: past volcanic eruptions

What are the two sources of current and future sea‐level rise?

1) Mostly related to melting of mountain glaciers 2) A large portion is also related to thermal expansion of ocean water related to global warming (but not related to ice melting)

What are four characteristics that are necessary for a tree‐ring sample to be suitable for crossdating?

1.has rings 2.distinct boundaries 3.sensitive growth 4.long ring record

What is a frost ring and what causes a frost ring to form?

A frost ring is a row of damaged cells in the middle of a tree ring--very cold temperatures cause the cell damage in the trees, more likely to happen for temperature-sensitive trees growing at high elevation

How are the mountain glaciers changing (relative to the ice sheets)?

Accelerates ice flow, Leads to total loss of ice sheet mass over time, contributes to sea-level rise

What information is shown by the longest ice cores from Antarctica?

Data from Vostok Ice Core (400,000 years) and Dome C (800,000 years), Shows repetitive cycles or fluctuations in CO2, increased CO2 in atmosphere in recent decades, high levels have never been seen before

what is proxy data?

Data that represents past environments and climates

What do the layers of pollen in a lake sediment core represent?

Different pollen assemblages represent different vegetation and climate in the past (based on modern analogs) and used to interpret climate changes (~10,000 years)

Where are the world's two ice sheets?

Greenland = 1.7 million km2 and Antarctica = 14 million km2

How long is the climate cooled following a volcanic eruption?

Lasts for 1 - 2 years

How do sunspots affect climate, specifically, how is the energy budget affected?

More sunspots = more incoming solar radiation, Earth's surface temperature increases

In the past 1,000 years, what is the evidence of warmer temperatures during the Medieval Warm Period?

Most of the evidence comes from northern Europe, ex: vikings settled in Greenland for about 400 years

What is the evidence of the Little Ice Age?

Mountain glaciers were more advanced in some locations than they are today (or earlier in the century)

What is sensitive tree growth?

Sensitive means that there is variation between wide and narrow rings and narrow rings

What modern measurements do scientists make in order to have a modern analog for an ice core?

Scientists take samples of the modern atmosphere, snow and ice at the location of the ice core. In many places, they have been monitoring CO2 and ice accumulation for the past 40 years

Climate variability

Short-term changes in the climate occurring over years to decades, usually related to natural climate forcings/influences

Does sunspot activity contribute to recent warming of the past few decades?

Sunspots only contribute a tiny amount to recent warming

Why is it important to learn about the climate of the past 1000 years? (i.e. graphic of northern hemisphere temperature reconstruction for past 1,000 years)

The key to the future is understanding the past, Historical information provides a context for recent warming, Help us to predict the future environmental conditions

What is the climate effect of a large, explosive volcanic eruption?

This blocks the amount of incoming solar radiation reaching the earth surface and cools the climate.

What are some examples of natural archives which contain proxy data?

Tree rings, Ice cores, Fossil pollen, Ocean sediments, corals

Why do trees grow distinct rings?

Trees grow from the inside out youngest rings on the outside.

What is a skeleton plot master and what information does it show?

a plot of narrow rings for a site (group of trees), plot shows the narrow rings with calendar years

How long does the climate effect last? (sunspots)

about 10 years

global warming

an average increase in the earth's surface temp related to increased fossil fuel emissions (same as climate change)

Did sunspot activity contribute to the cooler period of the Little Ice Age?

decreased sunspot activity may be partly responsible for cooler climates during Little Ice Age

What are two ways that Arctic sea ice has changed in the past 35 years?

decreasing in area, decreasing in thickness

What is the difference between Global Warming and Climate Change?

global warming is just one aspect of global climate change, refers to climate change that is related to human activities

enhanced greenhouse effect

increased greenhouse gases from fossil fuel emissions in the atmosphere have increased the greenhouse effect

How are they changing over the past 35 years?

increasing trend in extent of surface melting

Paleoclimate reconstructions (i.e. northern Hemisphere temperature of the past 1,000 years) use several types of proxy data.

lecture 21 slide 4

climate change

long-term changes in the regional climate or earth's average temperature occurring over decades to centuries (not only warming)

Greenhouse effect

longwave radiation absorbed and remitted back to earth by the greenhouse gases (CO2, H2O, CH4, N2O) in the troposphere

Understand what the hockey stick diagram (and related paleoclimate reconstructions) show

paleo)climate reconstruction-understand how much the climate has changed in the past and what influences past climate changes. Hockey stick-Dramatic warming in past few decades

What is significant about recent warming compared with the temperature of the past 1,000 years?

provide a context for recent global warming

How do volcanoes cool the climate? (summary slide with the cartoon of the energy budget)

reflects more incoming solar radiation

What is the difference between temperature‐sensitive and moisture‐sensitive tree growth?

temp: higher elevation, growth is limited by cold temperature Usually enough moisture (lots of snow), but trees need warm temperatures in the summer in order to grow moisture: At lower elevations, trees are limited by precipitation, Usually warm enough, but dry years (lack of rainfall) will limit growth

Climate

the average of many year's worth of weather for a location/region (i.e. the annual rainfall in Tucson is 12 inches)

And what does sensitive tree growth represent?

the basis for all tree ring dating and paleoclimate reconstructions

What environmental conditions influence tree ring width?

the width of a tree ring can be related to changes in a climate variable (i.e. temperature or precipitation) Trees growing in mountain environments (or any location with a winter season) In the winter, the tree shuts down and stops growing

Why are volcanoes near the equator the most effective at cooling the climate globally?

upper-level winds transport the volcanic gases and ash to cover both hemispheres

What is cross dating? (tree rings)

used for determining how old a sample is

What is a paleoclimate reconstruction?

using proxy data to represent the climate (average temp or precipitation) in the past (for a region or hemisphere)

What is the difference between Climate Change and Climate variability?

variability is short-term changes in climate over years/decades. climate change is long-term changes in regional climate or earth's avg. temp over decades/centuries

Where do Bristlecone pines grow?

very high elevations, The White Mountains of California

Would there be warming without the influence of human‐related influences on the climate (i.e. fossil‐ fuel emissions?)

yes

What is crossdating used for? Why is necessary?

you can match the growth pattern of older samples with modern samples and determine the age