# Presentation: 908724

## Climate Change:  The Physical Science Basis, Impacts, and Transportation’s Role

**Jeff Houk**
**FHWA Resource Center**

## Why is FHWA Concerned about Climate Change?

**1)  Impacts on transportation infrastructure**
**2)  Transportation contribution to greenhouse gas emissions**

## Climate Science--Introduction

**Climate change is a controversial topic that involves continuing research, debate and some uncertainty**
**FHWA relies on the expertise of other federal agencies (particularly NOAA, NASA and USGS), as well as the IPCC, to help guide our decisions regarding which issues to focus on and where to target resources**

## The greenhouse effect keeps Earth habitable, but recent changes to the atmosphere are causing it to warm.

- Source: USEPA

*The greenhouse effect keeps Earth habitable, but recent changes to the atmosphere are causing it to warm.*

## 1)  There is compelling evidence that Earth’s climate is changing.

## 2007 IPCC Reports

**In 2007, the Intergovernmental Panel on Climate Change released a series of updated climate assessment reports**
**Over 100 US scientists participated, including 9 lead authors from NOAA **
**IPCC web site: ****www.ipcc.ch/**

## Uncertainty in Climate Science

**Climate science is a complex field with many components featuring varying levels of scientific understanding**
**New information continuously surfaces**
**	**
**Researchers are generally:**
**	****Very confident in measured data**
**	****Pretty confident in projections of trends and global impacts**
**	****Less confident in projections of absolute numbers and localized impacts**

## Case Study in Uncertainty:  Hurricanes

**The atmosphere and oceans are warming, and a warming atmosphere contributes to warming oceans.  We know this based on both basic physics, and observations.**
**Warmer ocean water tends to strengthen hurricanes**
**Logically, further global warming would lead to stronger hurricanes, but there is still some debate about this.  **
**There is essentially no agreement about whether warming will lead to *****more***** hurricanes.**

## IPCC vocabulary:

***Virtually certain***** means more than 99% statistical certainty**
***Extremely likely/unlikely*****:****  greater than 95% certainty**
***Very likely, Very high confidence*****:****  greater than 90% certainty**
***High confidence*****:****  greater than 80% certainty**
***Likely*****:*****  *****greater than 66% certainty**
***More likely than not*****:****  greater than 50% certainty**

## 2007 IPCC Findings

**Average Northern Hemisphere temperatures during the second half of the 20th century were ****v*****ery likely****** (> 90% chance) *****higher than during any other 50-year period in the last 500 years and *****likely******  (> 66% chance) *****the highest in at least the past 1300 years.**

## 1000 years of “proxy” surface temperatures, 100+ from thermometers

## Global temperature has risen about 0.8°C over 125 yrs

**Source:  National Climate Data Center, March 2008**

## Changes in natural systems are occurring that are consistent with rising temperatures

**Some of the measured (not modeled) impacts include:**
**	****Net loss of glacial and sea ice**
**	****Rising sea level**
**	****Permafrost melt**
**	****Increases in heat waves, wildfires and floods**
**	****Increases in atmospheric water vapor**
**	****Changes in biological systems (shifting habitat zones, ****	****earlier leaf-out dates, shorter hibernation periods)**
**The 2007 IPCC report evaluated over 25,000 studies:**
**	****>90% show results consistent with warming**

##   There is compelling evidence that Earth’s climate is changing.2)  There is compelling evidence that human activities are influencing global climate.

## Influences on global climate

**NATURAL INFLUENCES**
**variations in the energy output of the Sun**
**variations in the Earth’s orbit and tilt**
**continental drift**
**changes in atmospheric composition from volcanoes, biological activity, weathering of rocks**
**HUMAN INFLUENCES**
**rising concentrations of greenhouse gases from deforestation, agriculture, fossil-fuel burning**
**rising concentrations of particulate matter from agriculture, fossil-fuel burning**
**alteration of Earth’s surface reflectivity by deforestation**
**increased high cloudiness from aircraft contrails**

- Holdren, WHRC, 2006

## 2007 IPCC Findings

**Most of the observed increase in globally averaged temperatures since the mid-20th century is *****very likely****** (> 90% chance) *****due to the observed increase in anthropogenic greenhouse gas concentrations. **
***Very high confidence***** *****(> 90% chance) *****that net effect of human activities since 1750 has led to global warming; *****extremely unlikely***** *****(< 5% chance)***** that observed temperature changes can be explained otherwise**

## Greenhouse Gases:  Carbon Dioxide

**CO****2**** is the major transportation GHG (about 95% of the overall impact) and is directly related to energy consumption**
**Atmospheric concentrations are growing every year because:**
**	****CO****2**** emissions are growing, and **
**	****CO****2**** has a long atmospheric lifetime (~100 years or more)**
**Unlike urban air pollution, which dissipates under the right weather conditions, CO****2**** accumulates in the atmosphere because plants and the oceans can’t absorb it fast enough**

## Other Greenhouse Gases

**Other gases also have long atmospheric lifetimes and are more potent GHGs than CO****2**** (they have a higher *****global warming potential*****):**

| Gas | Lifetime | GWP (relative to CO2) |
| --- | --- | --- |
| CH4 | ~12 years | 21 |
| HFCs | 1.5-264 years | 140-11,700 |
| N2O | ~120 years | 310 |
| SF6 | ~3200 years | 23,900 |
| CF4 | ~50,000 years | 6500 |

*EPA*

**The net impact of each gas on the atmosphere (*****forcing*****) is a function of **
**the amount of the gas released, and its global warming potential.**

## 400,000 years of greenhouse-gas & temperature history based on bubbles trapped in Antarctic ice 

**400,000 years of greenhouse-gas & temperature history based on bubbles trapped in Antarctic ice **
- Time scale expanded for last 150 years (right side of diagram)
- CO**2** & CH**4** are far above range of natural variation in current geologic era.

**Hansen,Clim.Change 68, 2005**

## Effective climate forcings

## 2007 IPCC Report Modeling Scenarios

- Black lines show actual temperature record; blue area shows modeled change with only natural forcings; red area shows modeled change with both natural and manmade forcings.

## 1)  There is compelling evidence that Earth’s climate is changing.2)  There is compelling evidence that human activities are influencing global climate.3)  What are the likely impacts if we don’t reduce GHG emissions?

## 2007 IPCC Findings

***Virtually certain***** *****(> 99% chance) *****that trend toward warmer weather will continue**
**With a doubling of atmospheric CO****2**** concentrations, temperature increase is *****likely***** *****(> 66% chance) *****to be in the range of 2 - 4.5 degrees C, *****very unlikely***** *****(< 10% chance) *****to be less than 1.5 degrees C.**

## Future Climate Projections

## Impacts of further temperature increases

**Existing impacts get worse**
**Climate “feedbacks” accelerate (e.g., melting permafrost releases methane, which causes more warming, which causes more melting . . .)**
**Conflicts emerge over drought-induced water shortages and population migrations due to sea level rise**
**Species impacts:**
**	****- some species lose habitat, others pushed to the limit of their range**
**	****- some animal species may migrate faster than their food source**
**	****- 20-40% of species at increased risk of extinction**
**Impacts on transportation systems from heat, sea level rise, storms**

## IPCC-Recommended Policy Goal

**To prevent the more serious consequences of climate change, the IPCC suggests that temperature increases should be limited to 2 – 2.4°C**
**This would require a 50-85% reduction in GHG emissions by 2050.**

##   There is compelling evidence that Earth’s climate is changing.2)  There is compelling evidence that human activities are influencing global climate.3)  What are the likely impacts if we don’t control GHG emissions?4)  What is transportation’s contribution to GHG emissions? 

## Transportation accounts for about 1/3 of US anthropogenic CO2 emissions

## Transportation energy use and CO2 emissions increased ~30% between 1980 and today

## Highway vehicles account for ~80% of total US transportation GHGs (global average is about 70%)

- EPA 2007 GHG Inventory

## US Transportation vs Global Emissions

| CO2 emissions from fossil fuel use
(2005 Million Metric Tons, %) |  |  |  |
| --- | --- | --- | --- |
|  | World | U.S. | U.S Transportation |
|  | 28,193 | 5,751 | 1,898 |
| % of U.S. |  |  | 33% |
| % of World |  | 20% | 7% |

## What can we do to reduce transportation emissions?

**1) Improve vehicle energy efficiency (fuel economy)**
**2) Reduce carbon content of fuels**
**3) Improve transportation system efficiency**
**4) Reduce VMT through better planning**
**5) Emissions trading and pricing strategies**
**6) Carbon sequestration**

## Conclusions

**Scientists have very high confidence that the Earth’s climate is changing, and that greenhouse gases from human activities are the major influence**
**The scientific community recommends a 50-85% reduction in GHGs by 2050 to avoid the worst impacts**
**Transportation is the largest single source of CO****2**** in the US**
**There are many options, including some that can be facilitated by FHWA, for reducing transportation GHG emissions**