ATMO 336 1st Edition Lecture 26Outline of Last Lecture I. New midterm materialOutline of Current Lecture II. Climate model forecastsIII. Predictions of equilibrium temperature after doubling CO2IV. Model predictions of temperature changes for the 21st centuryV. Climate model predictions for extreme weather eventsCurrent Lecture- Climate model forecastso Simulate earths climate and climate changes including changes due to increased greenhouse gas concentrations.o Are not perfect and do not make accurate predictionso Results of climate model simulations should not be the sole reason for enacting environmental policyo Been able to closely reproduce natural, short term fluctuations in climate due to historic events like volcanic eruptions and el Nino/ la ninao According to climate models, most of the measured increase in global average temp since 1900 was caused by increases greenhouse gaseso Climate models faikl to reproduce temporal (time) and spatial (position) variability that isknown to happen in the real world, especially over small scales.o Predictions of future climate change are more difficult than simulating past climate changes o Continuing to improve observations and understanding of climate system. However, should be viewed with skepticism- Predictions of equilibrium temperature after doubling CO2o Possibility that all climate models will be wrong Thus, we should consider all of them as possible outcomes of adding greenhouse gases.o The ability of global climate models to reproduce the observed surface temperature trendsover the 20th century represents an important test of the models the observed changes in climates at the scale of regional climate zones has not been reproduced by any climate model.o Climate models used to produce the 2013 IPCC Report all have positive feedbacks with respect to changes in carbon dioxide, since the most likely outcome is for global average temperature to increase by more than 1 degrees C.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Increasing the amount of greenhouse gases in the atmosphere, intially slows down the rateat which the Earth emits infrared radiation to space.o Assuming no change in energy input (Energy the Earth absorbs from the Sun), the Earth is no longer in energy balance since energy in exceeds energy out.o As long as energy in exceeds energy out, the planet warms. In particular the Earth's surface temperature will warm.o As the Earth's surface temperature warms, the amount of radiation energy it emits increases. Since some of this extra radiation energy is lost to space, thus the amount of radiation energy that the planet emits to space starts to increase.o The warming continues until the energy out increases to the point where it equals the energy input.o The Earth's surface is 70% covered by Oceans. Oceans have a high thermal inertia, so the Ocean surface temperature is slow to warm up in response to the energy imbalance caused by adding greenhouse gases to the atmosphere. The two main reasons for this is that (1) water has a high specific heat (meaning you have to add a lot of energy to liquid water to change its temperature in comparison to many other materials), and (2) the surface temperature of the ocean is slow to warm up because the additional heat must is able to mix somewhat through the entire depth of the oceans.o Therefore the amount of warming of the Earth's surface (temperature increase) required to bring the system back into balance (energy input equal energy output) will take quite some time.o As a result of the delay induced by the oceans, some climate scientists do not expect the Earth to warm by the full 1.5-4.5°C (2.7-8.1°F) by 2060, even though the level of CO2 is expected to have doubled by that time- Model predictions of temperature changes for the 21st centuryo Even if concentrations of all greenhouse gases had been kept constant at year 2000 levels,a further warming of about .1 degrees C would still be expected due to the ocean delay.o First IPCC report= projected warming of global average teps of between .15 and .30 degrees C per decade from 1990- 2005.o Most climate models have predicted far too much warming of global average surface temperature since the early 2000s. reasons: Lack of warming since 2002 due to natural variability energy or heat is currently being stored in the deep oceans instead of warming thegreenhouse gases models are wrong; real climate is not as sensitive to changes in CO2 as the models predict (may be dominated by positive feedbacks)o currently, the intergovernmental panel on climate change (IPCC) projects a warming of .3-4.8 degre3es C (.5-8.6 degrees F) in global average temperature for the last two decadesof this century (2081-2100) relative to the average temp for 1985-2005. Based on best global climate models and the several estimates of future emissionsof greenhouse gases. In spite of these, climate models have major problems in reproducing the multidecadal climate variability that is kown (through observations) to take place at regional (ecosystem level) scales- Climate model predictions for extreme weather eventso Information from latest IPCC report Total # of frost days Intra annual extreme temperature range (difference between highest and lowesttemps over calender year) Growing season length Heat wave duration index (longest stretch of days with high temps at least 9 degrees F warmer than then 1961-1990 average high temp) IPCC says there will be an increase in the number and severity of heat waves worldwide Warmth of daily lows Wet days Dry days Wet stretches Average daily precipitation intensityInfluence of wet days on annual total (percentage of total precipitation occurring on days that exceed the 95th percentile from 1961-1990 average) IPCC predicts it is very likely to have increase in extreme precipitation events over most mid-latitude land masses as well as wet tropical