CE 401 Climate Change Science and Engineering Climate Change Science (in one lecture) 13 January 2011 homework 2: use the Mauna Loa data on the class website to graph the annual average increase/decrease in atmospheric CO 2 (in %) from 1959 to Read Chapter 1 of Houghton. Due Thursday, 1/20

note – as this talk on climate science procedes: be skeptical look hard at the data ask questions !!!!!!!!!!!!!!!! don’t be misled the debate is polarizing and political the implications of action are controversial and expensive

Revelle and Suess (1957): “human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future. Within a few centuries we are returning to the atmosphere and oceans the concentrated organic carbon stored in sedimentary rocks over hundreds of millions of years”

Outline introduction greenhouse gases and Earth temperature evidence for climate change in the past evidence for current climate change climate change, policy makers, and climate models predicted effects of climate change some thoughts on global energy usage

temperature structure of the Earth’s atmosphere

composition of the Earth’s atmosphere

solar and earth spectra

Greenhouse Gases H 2 O - by far most important GHG - ~ 60% of total GH effect CO % of human produced GHG effect e.g., an automobile with 20 mpg fuel economy produces ~ one pound CO 2 per mile --> 7 tons/yr at 15K miles/year preindustrial conc. = 260 ppm, current conc. 390 ppm mostly produced by industrial/transportation sectors CH 4 - methane 25% of human GHG effect preindustrial conc. = 0.7 ppm, current conc. 1.7 ppm biomass burning, landfills, animal/human waste N 2 O - nitrous oxide 5% of human GHG effect cultivated soils, industrial, biomass burning, feedlots

Thursday, 13 January questions from last time??? overview of climate change science HW #2: use the Mauna Loa CO 2 data on the class website to graph the annual average increase/decrease in atmospheric CO 2 (in %) from 1959 to Show all your work and state your assumptions Read Chapter 1 of Houghton Due Thursday, 1/20

Greenhouse Gases (GHG) and Energy Balance GHG transmits light (energy) well in the visible part of the spectrum where the Sun (T eff ~ 5700K) produces most of its energy GHG is relatively opaque in the infrared part of the spectrum where the Earth radiates most of its energy (10µm ~300K) this “blanket” of gases insulates the Earth the radiation coming in from the Sun must still be radiated out  the Earth reaches a higher equilibrium temperature than w/o GHG Earth is ~ 33°C warmer than w/o the atmosphere solar spectrum to 3µm

Global Change due to Human Influence is a Reality air and water pollution burning of fossil fuels industrial activity transportation electrical generation changing land use vegetation urbanization desertification biomass burning wetland destruction

Weather and Climate weather occurs over a relatively short time scale (days, weeks, months) climate is the average weather over years, decades, centuries causes and effects of climate change are generally in the troposphere, the bottom 10 km of the atmosphere

CO 2 increases are clearly human induced and are accelerating current increase is about 1.9 ppm/year (not subtle) CO2: pre-industrial : 280 parts per million; current: 392 ppm; 38% change in 50 years

What Processes Control Atmospheric CO 2 ? Only ~ half of the CO 2 produced by human activities remains in the atmosphere CO 2 is not reactive and lives a long time in the atmosphere where are the sinks of CO 2 - ocean, forest, …?

Evidence for Climate Change in past not human induced

The atmospheric concentration of CO 2, N 2 O, and CH 4 now exceeds by far the natural range of the last 650,000 years - current changes have occurred all in a few hundreds of years CO 2 CH 4 N2ON2O time (thousands of years before present) note

Current level is higher than any time in past 600,000 years. 150,000 years ago to present

this graph  dramatic evidence that CO 2 drives climate: more CO 2  higher temperatures. YES? Here is Al Gore on this graph: “Here is an important point. If my classmate from 6 th grade were to see this, he would ask, “Did they ever fit together?”. The answer from the scientist would be, “Yes, they do fit together.”. It’s a complicated relationship, but the most important part of it is this: When there is more CO 2 in the atmosphere, the temperature increases because more heat from the sun is trapped inside. There is not a single part of this graph – no fact, no date, or number – that is controversial in any way or is disputed by anyone.” What is cause and effect? The implication here, honestly stated by Gore, but implied, is more CO 2, higher T Yet, many scientists think the opposite: large changes in CO 2 were a result of the warming, not the cause. Changes in temperature in this graph were driven not primarily by CO 2 changes, but by changes in the orbit and axis of the Earth. Caillon et al, 2003, Science 299, 1728  CO 2 lags behind temperature changes by about 800 years years (why 800 years?) Some climate scientists now doubt the order. Richard Muller (Physics for Future Presidents, 2008)  “The fairest statement that can be made is that the issue is unsettled”. “Many people see the plot and come away believing that CO 2 has been established as the main driver for past climate change. That is very likely a correct conclusion for small (1°C) changes attributed to the present CO 2 increase, but not clear for the dramatic temperature variations of ancient data shown in the plot”

source: Jouzel et al °C 5°C age (thousands of years ago) Antarctica Greenland North Atlantic Antarctic and Greenland Ice Core and N. Atlantic Sed. Temp. Data note how stable temperature has been for the last 10,000 yrs

HOCKEY STICK PLOT Mann et al, 1998

hockey stick: published in 1998 NH remarkably constant showing cool years with significant global warming occurred 2001 IPCC report included it – 5 times in the summary volume alone prominently featured in Al Gore’s film showed the modern fossil fuel era was unprecedented in increased temperature just like the CO 2 rise plot  patently obvious that humans were causing warming Canadian gov’t sent a copy to every household in Canada every politician in DC was familiar with it 14 th century COLD period appears nowhere in the plot (it was European only?), but that cold period is well established the graph is wrong – the analysis has proved to be faulty and really only represents western US, not the northern hemisphere US National Academy of Sciences was asked by Congress to review  confirmation of error does it matter that the hockey stick plot was wrong? yes, it reinforces misconceptions to a scientist, it is wrong, but it is just another step in the process IPCC consensus did not depend on the hockey stick graph of temperature vs time it is embarrassing for sure scientists usually reach the truth, but sometimes it takes a while

CO 2 concentrations are increasing due to industrial activity CO 2 Concentrations (ppm)

the sun and climate

Solar variability and late 20 th -century Warming satellite measurements of solar brightness 0.1% variation

natural variations in climate are caused by (at least): changes in the radiation balance of the Earth-Sun system intrinsic changes in solar flux long term - must be modeled using sunspot numbers solar cycle - only two cycles measured % changes in Earth orbital parameters - Milankovitch cycles periods of 20k - 100k years explain all the major ice ages – dramatic changes in temperature changing aerosol concentrations (e.g. volcanic activity)

Conclusions from the Climate Record preindustrial to 650k years ago (no human influence) temperatures have varied by approximately 7°C highest observed CO 2 is about 300 ppmv (current 385 ppmv) highest observed methane is about 0.7 ppmv (current 1.7 ppmv) temperature, CO 2 and methane follow each other closely in time changes have generally occurred over long time periods past 10K years have been remarkably stable in temperature this period marked the development of civilization most “equable” climate of the past many millions of years rapid (decadal) changes in surface temps of 5-6°C have occurred in the past

Evidence for Current Climate Change

US surface temperature record

Global Mean Temperatures Annual mean Smoothed series 5-95 decadal error bars source: IPCC = Intergovernmental Panel on Climate Change, of the past 12 years are the hottest on record

last decade is the warmest decade on record increase in past 25 years is ~ 0.2°C/decade NASA Global Temperature Record source: GISS, 2010

NOAA (12 JAN 2011)  2010 tied 2005 as the hottest year on record

detection of significant change is a statistical problem: finding a small signal in a sea of poorly understood noise the instrumental record is short --> rely on proxy measurements changes have obviously occurred over the past 100 years that are not human related warming 1970s cooling if an observed change in the record is judged unlikely to have occurred due to natural processes --> implicates human factors (???) assignment of attribution to a human cause requires consideration and elimination of all plausible non-human mechanisms can’t eliminate all plausible mechanisms cause and effect are usually approached with a series of controlled experiments, but this cannot be done in this case experiment is not systematic - too many parameters are being changed at one time

What are some of the problems with these graphs of surface temperature vs time? There are lots of problems with these graphs!! What are possible problems?????

urban heat island effect California surface weather stations Robinson et al (2007): Surface temperature trends from 107 measuring stations in 49 CA counties. Trends combined for counties of similar population. The “X” show the stations used by NASA GISS for their estimate of global surface temperatures. Such selections make the NASA GISS modeled temperatures too high. original source: F. Singer, Hot Talk, Cold Science, 1997 California weather stations

where is temperature data collected (geographic distribution) how is temperature collected? (same method everywhere?) what affects the reading of the thermometer? (surroundings) consistency of measurement method over a period of years

sea surface temperature source: IPCC 2007 what are potential problems with this graph? red = observations models

red: reconstructed sea level fields since 1870 (Church and White, 2006) blue: coastal tide measurements since 1950 (Holgate/Woodworth 2004) black: satellite altimetry (Leudiette et al, 2004) sea level change source: IPCC 2007

Figure m layer. shading = 90% confidence. Global ocean heat content source: IPCC 2007

Snow cover and Arctic sea ice are decreasing (area vs time) Spring snow cover in millions of square km present Arctic sea ice area decreased by 2.7% per decade source: IPCC, 2007 glaciers are retreating

Figure 4.22 variations in monthly areal extent of seasonally frozen ground for in NH, smoothed source: IPCC 2007

POLICY MAKERS ARE INTERESTED IN THE FUTURE What will happen and what is the cause? Models are used to predict future climate How well do these models predict the past? Can we trust models to predict the future? Decisions are based on the models!

source: IPCC 2007 The Climate System - very complicated

What Goes into Atmospheric Climate Models mathematical equations to describe air motion and processes solar flux and its changes in time - Earth energy balance clouds - largest source of uncertainty in the models 61% of the globe on average is covered with clouds clouds both reflect energy (cooling) and serve as thermal blankets (warming) Earth reflectivity (land, sea/water, ice, snow, vegetation, etc.) thermodynamics of water and radiation chemistry and carbon cycle (atmosphere, oceans, biosphere) anthropogenic contributions (e.g. CO 2 increases with time, biomass burning, land use changes, etc.) aerosols which cool the atmosphere (natural and anthropogenic)

The atmospheric models must be coupled to: cryosphere biosphere oceans hydrosphere all on a high resolution global spatial grid of latitude and longitude and altitude as a function of time and incorporating the many feedback mechanisms that control atmospheric processes This is a huge job that requires experts from many fields and a large computer! There are a number of groups around the world working on this problem.

Observations Natural + Human-induced With human-induced influence Observations and Model Comparison Temperature Change, Present Natural Without human-induced influence black = observations red = modeled natural + human blue = modeled natural alone

IPCC 2007

The Current Scientific Consensus ( remember that science is not about consensus) IPCC, 2007: “the observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 years can be explained without external [human] forcing, and very likely that it is not due to known natural causes alone.”

Projected changes in annual temperatures for the 2050s The projected change in annual temperatures for the 2050s compared with the present day, when the climate model is driven with an increase in greenhouse gas concentrations equivalent to about 1% increase per year in CO 2 BW 11 source: GISS

-30% %

South Florida: 1-m rise in Sea Level

Change in January Average Daily Maximum Temperature (doubling of CO 2 ) source: Hotchkiss and Stone (2000)

Present CO 2 doubling by 2050 Vegetation Changes for Modeled Doubling of Carbon Dioxide source: IPCC, 1996 Temperate forests Grasslands Deserts Savanna Tropical seasonal forest Tropical moist forest Ice Tundra Boreal forests Color Code: now x 2 CO 2

Global Energy Useage industrialized nations 20% of population 75% of carbon emitted since 1950 ~< 50% of today’s carbon emissions developing nations 80% of population 25% of carbon emissions since 1950 ~> 50% of today’s emissions economic & population growth --> huge emissions increases

country on lower axis – which one is the US?

toe per capita

by region; mtoe = million tonnes of oil equivalent

summary: GHG concentrations are increasing without any doubt whatsoever – it is not subtle the cause of the GHG increase is clearly human caused there is little debate that climate warming is occurring the debate centers on the causes of the debate – is it natural or human-caused the Earth climate system is very complicated the science is never complete and there will always be intelligent questions climate is difficult to model and make predictions, but the models are what we have the majority of models predict significant changes in average Earth temperature the rhetoric is polarizing the politics is loud and divisive should policies be put in place to limit the growth of GHG? These policies will radically change fossil fuel combustion as a source of energy what can engineers contribute to the changes that will be coming?