# Presentation: 213629

## U.S. Climate Change Science Program: Planning Workshop for Scientists and Stakeholders

**U.S. Climate Change Science Program: ****Planning Workshop for Scientists and Stakeholders**

- Thomas R. Karl
- National Oceanic and Atmospheric Administration
- National Environmental Satellite Data and Information Service
- National Climatic Data Center
- Asheville, NC 28801-5001, USA
- December 4, 2002

## Thanks

**John Christy**
**Ben Santer**
**Frank Wentz**
**Dian Seidel**
**John Lanzante**

**Kevin Trenberth**
**Mitch Goldberg**
**John Bates**
**David Easterling**
**Carl Mears**

***Thanks***
**The following helped articulate this issue:**

## Tropospheric temperature increase 
Stratospheric temperature decrease
Surface temperature increase 
Tropical troposphere warms more than surface 

What do observations show?
Since 1960 surface and troposphere warm about same rate
Since 1979 surface warms more than troposphere 

- Tropospheric temperature increase
- Stratospheric temperature decrease
- Surface temperature increase
- Tropical troposphere warms more than surface
**What do observations show?**
- Since 1960 surface and troposphere warm about same rate
- Since 1979 surface warms more than troposphere

**With more greenhouse gases climate model project**

**Is the surface really warming more than the troposphere?**
-  		Are observational errors non-trivial?
-  		Have we inaccurately specified important forcings?
-  		Inadequate model physics?
-  		Combination of all of the above?
**NRC (2000) & IPCC (2001) assessment**
-  	NRC ---- 0.1C/decade uncertainties in the 		trends of tropospheric temperatures
-  		IPCC reported 	_**Since 1960**_
-  	0.2 to 0.4°C tropospheric temperature increase (similar to the surface)	_**Since 1979**_
-  	0.3 to 0.4 °C temperature **increase** near the surface
-   0.0 to 0.2°C temperature **increase** in the low-to-mid troposphere
-  	0.5 to 2.0°C temperature** decrease** in the stratosphere
-  	Significantly different trends of temperature between the surface and 										troposphere

## New analyses since IPCC & NRC reports

**New analyses since IPCC & ****NRC reports**
**Tropospheric Temperature Trends**
_**Radiosondes**_
-  	Trends based on radiosondes 		yield different results (little or no warming 		to 	0.2°C/decade since 1958)
_**Satellites**_
-  	Another updated and revised satellite-based analysis 		has only a small, statistically insignificant, positive trends
- A new analysis of the satellite record (since 1979) 		indicates warming in the troposphere > 0.1°C/decade

## New analyses since IPCC & NRC reports 

**New analyses since IPCC & NRC reports**** **
**Surface Temperature Trends**
**Model Simulations**
-  	New model simulations unable to simulate the largest 	differences in observed trends between surface 	and troposphere
**Where are we today?**
-  	Differential rates of temperature change in the atmosphere remains 	a complex issue

_**Since late 1970’s:**_
-  	Numerous analyses: global surface temperature 	increases of >0.15C/decade
-  	Supported by ancillary data such as snow cover 	and sea ice reduction, permafrost changes, lake 	and river ice freeze/thaw dates, etc.

##  	Existing dilemma traced to 	the 1990 pioneering work of 	Spencer and Christy

-  	Existing dilemma traced to 	the 1990 pioneering work of 	Spencer and Christy
-  	UAH Team (University of 	Alabama at Huntsville) took 	advantage of the Microwave 	Sounding Unit (MSU) aboard 	NOAA polar orbiters.
-  	UAH found that satellite-	derived global tropospheric 	temperatures had 	negligible warming
** ****	****Disparity with surface ****	****warming**

- Prepared for IPCC (2001)

## MSU2LT

- MSU channels and their atmospheric weighting functions used on NOAA operational satellites since 1979 (from Christy, 2002).

_**MSU2LT**_
-  Derived by differencing view-angles (UAH)
** ****	****Lowest layers:** microwave data affected by changes in 	surface emissivity
-  	Subject to increased noise over mountainous terrain, 	e.g., Himalayas, Greenland, Antarctica
_**MSU2**_
-  	Tropospheric temperatures contain some stratospheric 	emissions
_**MSU2LT**_
- 	Trends show marked cooling in the lower stratosphere
-  	linked to ozone depletion and increases in 	greenhouse gases (IPCC, 2001).
-  	Such trends influence MSU2
_**Bottom Line**_
-  	Understanding the causes of stratopheric trends linked 	to 	understanding tropospheric and surface trends.

##   Why are adjustments so large?

**  ****Typical MSU channel 2 anomalies with and without satellite intercalibration.**** **

- (From Goldberg, 2002)

**  ****Why are adjustments so large?**

** ****Difficulties in piecing together a homogeneous temperature record**
-  	13 separate satellites 1979-2002 – all have varying degrees of overlap
-  	No on-board calibration
-  	Orbital drift and decay affects each satellite differently
-  	Wentz team (Remote Sensing Systems – RSS) discovered and corrected for 	orbital decay
-  	Also applied by UAH (versions D & 5) of their data sets

- Local equatorial crossing time for NOAA satellites show the long-term drift

- Ascending LECT (Hrs.)

- Simulated MSU2 mean diurnal amplitude for the June, nadir view

** ****Time of observation biases**
-  	UAH rely on overlapping measurements
-  	RSS use climate model simulations
-  	Observation time bias corrections over the oceans are small

- Wentz, 2002

##  	Temperature trends (1979)

-  	MSU2LT (surface to about 400hPa) 0.06oC/decade (version 5 from UAH)
-  	MSU2 - - 	UAH: 0.01oC/decade (version 5)				RSS: 0.12oC/decade (version 1)
-  	NOAA 9 ~ 65% of total difference of the two MSU2 trends
-  	RSS and UAH - - sharing data and algorithms to help explain difference
** ****	****Difficulty of adequately resolving the temperature issue attested to by the ****	****number of revisions (5) and the magnitude of the corrections required**

## Time dependent biases result from changes in:

- Degree of agreement between five research teams (adapted from the et al., 2000)

**Time dependent biases result from changes in:**
-  Instrumentation
-  Site location

-  Ground station processing
-  Proprietary calibration and adjustments

##  	Estimates of radiosonde based trends of temperature vary 	considerably

** ****	****Estimates of radiosonde based trends of temperature vary ****	****considerably**
** ****	****General agreement:**** Tropical troposphere warms in relation to ****	****the surface (1960-78) and cools thereafter**
** ****	****Most analyses show that there was a step change around ****	****1976-77, just prior to the satellite record**

##  	UAH compares satellite data with radiosondes & Reanalysis 	

** ****	****UAH compares satellite data with radiosondes & Reanalysis ****	**
-  Similarity of trends bolsters confidence of UAH record
-  Are the two data sets independent?
** ****HadRT** – uses MSU2LT to adjust
** ****MSU2LT** correction path guided by radiosonde comparison?

*Preliminary from Seidel (2003)*

## Tropospheric and surface temperatures from various research teams, (compiled by Christy and Easterling, 2002)

- Tropospheric and surface temperatures from various research teams, *(compiled by Christy and Easterling, 2002)*

*Step change around the time of satellite record*

## Providing a physical basis for differential rates of warming 

**Providing a physical basis for differential rates of warming **
- 	Analysis of model simulations
-  Differences of spatial coverage (satellite and surface observations)
-  Other forcings, e.g., volcanic eruptions and stratospheric ozone depletion
-  Modes of natural internal variability
_**Spatial Coverage**_
-   	Incomplete spatial coverage of surface explains ~ 1/3 of the difference (1979-	99) Santer et al. (2000), but ...
-  	Blended space-based/in-situ global surface data sets provide near-global 	coverage
-  	Does difference disappear with more comprehensive coverage?

## }

_**Uncertainties Arise from**_
-  	Knowledge of the volcanic and ozone forcings
-  	Errors in the model responses to these forcings
-  	Short length of the MSU record
-  	Difficulties in deconvolving effects of volcanoes and ozone depletion from 	ENSO variability
_**Bottom Line**_
-  Accounting for
-  	Coverage differences
-  	Volcano and ozone forcing
-  	Natural internal variability

**Providing a physical basis for differential rates of warming**
_**External Forcings Recently Considered**_
-   	Timing of recent volcanic eruptions
-  	Stratospheric ozone depletion
-  	Timing of ENSOs (minor)

*Helps to explain some, but not all of the differential warmings (from UAH and radiosonde)*

*Explains part of the difference (cooling of troposphere relative to surface) *

## Some Data Consistent With Models?

**Some Data Consistent With Models?**

- GHG, sulfates, ozone *(volcanic and ENSO removed from data)*

**Model Physics/Chemistry or Forcings Inaccurate?**

- From Santer (2002)

- 6 Ensembles (from Tettetal , 2002)

- Atmospheric Model forced with: GHG SST, O3 volcanoes, solar, aerosoles

## Improving observing systems and the data record 

**Improving observing systems and the data record**** **
- 	Transform the GCOS upper air network **(GUAN)** into an **Upper Air ****	****Climate Reference Network (UACRN)** following NRC monitoring 	principles
-  	Investigate the development of remote, unmanned systems to 	monitor upper air properties, e.g., pilotless aircraft
-  	Adhere to the **GCOS Satellite Monitoring Principles:**
**	**

-  	Facilitate access to products, 	metadata, and raw data
-  	Continue baseline instrument 	observations on decommissioned  	satellites
-  	Need in situ baseline observations
-  	Real-time monitoring of observing 	system performance

-  	Minimize orbit drift
-  	Ensure sufficient overlap
-  	Replace prior to failure
-  	Rigorous pre-launch 	characterization
-  	Adequate on-board calibration
-  	Operational production of 	priority climate products

## Improving observing systems and the data record 

**Improving observing systems and the data record**** **
- 	More focus on calibration issues during the NOAA-9 period
-  	Valuable ancillary data from MSU channel 1 and HIRS
-  	High-altitude, mid-troposphere GCOS **Global Surface ****	****Network ****	****(HA-GSN)** e.g., N. & S. American mountains to the Antarctic 	Peninsula, Pyrennes to Himilayas
-  	Ensure near-real time delivery of global temperature datasets
-  Established teams with peer-reviewed methodology

## New modeling simulations  

**New modeling simulations **** **
- 	Simulate the spatial and temporal sampling of the actual record of the 	NOAA satellites
-  	Ensemble simulations (last 50 years) from key climate models
-  Inclusion of both natural and arthropogenic forcings
-  	New Reanalysis model simulations
-  Including the analysis of the output for time-dependent biases