Modern Global Climate ChangeModern Global Climate Change

by Thomas R. Karl and Kevin E. Trenberthby Thomas R. Karl and Kevin E. Trenberth

Summary: Ken HuSummary: Ken Hu

Critique: Roy ChenCritique: Roy Chen

SummarySummary

AbstractAbstract of of thethe article article

• The article illustrates the relationship The article illustrates the relationship between human influences and modern between human influences and modern global climate change. It also predicts the global climate change. It also predicts the future base on the past information and future base on the past information and global climate models.global climate models.

Main DescriptionsMain Descriptions

• Human influences on climate Human influences on climate

• The resulting temperature and The resulting temperature and precipitation changeprecipitation change

• The time scale of responseThe time scale of response

• Important processes involvedImportant processes involved

• Climate modelsClimate models

• Observation and information systemsObservation and information systems

Human Influences on climateHuman Influences on climate

• Global Climate changeGlobal Climate change

• Regional Climate changeRegional Climate change

Global Influences changeGlobal Influences change

• Greenhouse gases increase Greenhouse gases increase

• Aerosols are removed Aerosols are removed

Greenhouse gases increaseGreenhouse gases increase

• Reason(s): Burning of fossil fuels and Reason(s): Burning of fossil fuels and methane and nitrous oxide from methane and nitrous oxide from multiple human activities.multiple human activities.

• For example: Carbon dioxide has For example: Carbon dioxide has increased 31 since preindustrial timesincreased 31 since preindustrial times

• Half of the increase has been since Half of the increase has been since 1965.1965.

• Result(s): global warmingResult(s): global warming

CO2 and T (Global) VS TimeCO2 and T (Global) VS Time

Aerosols are removedAerosols are removed

• Reason(s): Fuel burningReason(s): Fuel burning

• Results(s): Results(s):

1. Either net cooling or net heating1. Either net cooling or net heating

2. Directly reflecting solar radiation and 2. Directly reflecting solar radiation and indirectly by changing the reflective indirectly by changing the reflective properties of clouds and their lifetimeproperties of clouds and their lifetime

Regional Climate changeRegional Climate change

• Changing in landuse.Changing in landuse.

• Reason(s): Urbanization and agricultural Reason(s): Urbanization and agricultural practices.practices.

• For example: Large-scale deforestation and For example: Large-scale deforestation and desertification in Amazonia and the Saheldesertification in Amazonia and the Sahel

• Result(s): “concrete jungle” and its effects Result(s): “concrete jungle” and its effects on heat retention, runoff, and pollution, on heat retention, runoff, and pollution, resulting in urban heat islands.resulting in urban heat islands.

Human influence on global climate Human influence on global climate affects worldwideaffects worldwide

• Global warningGlobal warning

• Surface moistureSurface moisture

• Land-surface dryingLand-surface drying

• More atmospheric water vaporMore atmospheric water vapor

Human influence on global climate Human influence on global climate affects regionallyaffects regionally

• Wild fireWild fire

• Heat stressHeat stress

• Vegetation changesVegetation changes

• Sea level riseSea level rise

The time scale of response and The time scale of response and important processes involvedimportant processes involved

• Human-induced climate change is Human-induced climate change is projected to be much faster than most projected to be much faster than most natural processes.natural processes.

• Freshwater dischargesFreshwater discharges

• Greenland and Antarctica may not be Greenland and Antarctica may not be stable Raising sea levelstable Raising sea level

Concepts of the climate systemConcepts of the climate system

• Climate system is complicatedClimate system is complicated

• Three major feedback affect the climate Three major feedback affect the climate systemsystem

• Water vapor feedbackWater vapor feedback

• Cloud feedbackCloud feedback

• Ice-albedo feedbackIce-albedo feedback

Climate modelsClimate models

• The primary tools for predicting future The primary tools for predicting future climateclimate

• Fully coupled, mathematical, computer-Fully coupled, mathematical, computer-base models of physics, chemistry, and base models of physics, chemistry, and biology of the atmosphere, land surface, biology of the atmosphere, land surface, oceans and cryosphere and their oceans and cryosphere and their interactions with each other and with the interactions with each other and with the sun and other influences.sun and other influences.

Example of a modeling the climate Example of a modeling the climate systemsystem

Two Two atmosphere-ocean systematmosphere-ocean system

• El NiñoEl Niño

• North Atlantic Oscillation (NAO)North Atlantic Oscillation (NAO)

• El Niño is linked to the global heatingEl Niño is linked to the global heating

• NAO affects the severity of winter NAO affects the severity of winter temperatures and precipitation in Europe temperatures and precipitation in Europe and eastern North America.and eastern North America.

Observation and information Observation and information systemssystems

• Simulate the past climateSimulate the past climate

• ComprehensiveComprehensive

• Long term climate-related data setsLong term climate-related data sets

• Observing systems that deliver data free of Observing systems that deliver data free of time-dependent biasestime-dependent biases

• Global monitoringGlobal monitoring

Space-basedSpace-based

Surface-basedSurface-based

Conclusion of the articleConclusion of the article

• The article describes that we need better The article describes that we need better observation and system to project the observation and system to project the future global climate change. The climate future global climate change. The climate change is international greatest challenge.change is international greatest challenge.

Critique:Critique:

Author CredibilityAuthor Credibility

Thomas R. Karl Thomas R. Karl • Director of the NOAA National Climatic Director of the NOAA National Climatic

Data Center, in Asheville, N.CData Center, in Asheville, N.C• Fellow of the AMS and the American Fellow of the AMS and the American

Geophysical unionGeophysical union

Kevin E. TrenberthKevin E. Trenberth

• Fellow of the American Meteorological Fellow of the American Meteorological Society (AMS) Society (AMS)

• Fellow of the American Association for Fellow of the American Association for Advancement of Science.Advancement of Science.

Author Opinions: Author Opinions:

• Climate change is a global issue.Climate change is a global issue.• Human activities alter the climate change. Human activities alter the climate change.

For example, global warming effect that For example, global warming effect that results from the burning fossil fuels results from the burning fossil fuels (energy uses). (energy uses).

• We are entering the unknown with our We are entering the unknown with our Climate.Climate.

• We need improve climate observing in We need improve climate observing in order to analyze the global climate order to analyze the global climate change.change.

• Climate change may be our greatest Climate change may be our greatest challenge. We should work together to challenge. We should work together to overcome this challenge (global overcome this challenge (global Cooperation and action.Cooperation and action.

Paper StrengthPaper Strength

• Well developed and organized.Well developed and organized.

• First, authors analyze the some factors First, authors analyze the some factors cause the climate change. cause the climate change.

• Greenhouse gases emission and Greenhouse gases emission and landscape change ( from humans activities landscape change ( from humans activities directly) directly)

• Climate change complicated and amplified Climate change complicated and amplified by water vapor, cloud, Ice-albedo feedback by water vapor, cloud, Ice-albedo feedback

• NAO and El Niño. ( Ocean current NAO and El Niño. ( Ocean current systems) systems)

• Second, authors discuss the challenges to Second, authors discuss the challenges to analyze uncertainty of climate change.analyze uncertainty of climate change.

• Scientists need to improve observing Scientists need to improve observing systems and global simulation model by systems and global simulation model by integrate technologies.integrate technologies.

Paper weaknessPaper weakness

• Authors did not discuss the efforts to stop Authors did not discuss the efforts to stop global warming effect. For instance, U.N global warming effect. For instance, U.N global climate treaty.global climate treaty.

• U.S did not to produce significant U.S did not to produce significant reduction in greenhouse gas emissions, reduction in greenhouse gas emissions, which cause global warming.which cause global warming.

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