New U.S. Report of Global Climate Change: Some Thoughts
Posted: Fri Aug 27, 2004 12:33 pm
A look at this new report reveals some information that adds to credibility to the idea that there is a human contribution that, when combined, with natural climatic change helps explain the warming that has occurred during the 20th century.
The report states:
Multiple ensemble simulations of the 20th century climate have been conducted using climate models that include new and improved estimates of natural and anthropogenic forcing. The simulations show that observed globally averaged surface air temperatures can be replicated only when both anthropogenic forcings, e.g., greenhouse gases, as well as natural forcings such as solar variability and volcanic eruptions are included in the model.
<img src="http://www.usgcrp.gov/usgcrp/images/ocp2004/images/OCP04-05_fig9.jpg">
I believe this conclusion is reasonable. At this time, it is still unclear as to what share of the climate change is attributable to natural factors and what share is attributable to human ones. This report notes that both are involved but does not attempt to blame one or the other type of factor for most of the warming that has occurred. It does acknowledge that most of the pre-1950 warming was due to natural factors.
I will note that the PCM model which was employed to generate the above graph still leaves much to be desired. It deals with only a select number of natural forcings (volcanic and solar) but does not appear to incorporate additional cyclical variables such as ENSO, PDO, etc., if the key at the bottom of the chart is to be taken at face value.
As a very quick illustration of the importance of ENSO data, among others, for assessing climate change the following are two graphs:
<img src="http://www5.wright-weather.com/bb/attachment.php?s=&postid=300445">
1) The top graph illustrates the global mean temperature since just after 1880.
2) The bottom graph illustrates the 30-year moving average of the anomaly in ENSO Region 3.
In general, it appears that when the 30-year anomaly is "warm", the global temperature tends to be in a cycle where it tends to decline. When the 30-year anomaly in this region is "cool," the opposite is true.
There also appears to be a short lag between the 30-year anomaly and response in the global temperatures.
Notice that from around 1970 to the late 1990s, there was an especially pronounced "cool" period in the 30-year anomaly for Region 3. During this time, the global temperature rose especially sharply.
Now, a few years after the 30-year ENSO 3 anomaly has begun to move into "warm" territory, the global temperature may be showing indications of cooling.
Needless to say, this information does not argue against any impact from a buildup of CO2 in the atmosphere. Rather, it argues that incorporation of ENSO data, not just from Region 3, could add significant value in understanding global climatic trends.
On the matter of ENSO data, the report states:
A new multi-year assimilation of in-situ and satellite data into an ocean model highlighted the importance of the interior ocean mechanisms (as compared to boundary currents such as the Gulf Stream) on timescales of weeks to months. Investigators found these mechanisms in the interior ocean play a critical role in altering the water mass exchanges between the midlatitude eastern Pacific Ocean and the the tropical Pacific where El Niño develops, suggesting that remote effects on El Niño should be more carefully considered by prediction models. Further, these relatively fast mechanisms were found to govern more generally the transports and exchanges between the tropical and midlatitude ocean and thus could be an important factors for observing and modeling the longer-term changes (e.g., interannual to decadal variability) of the Pacific Ocean.
Unlike the two previous reports on which I commented--the California projections and the European ones--this report signals that important research that I would like to see (paleoclimatic) is underway.
It declares:
Based on a new synthesis of data from the Holocene Thermal Maximum (~9,000 years ago), warming is asynchronous and asymmetric across the North America Arctic region. Warming begins in the west and sweeps eastward. A georeferenced database of annually resolved records of Arctic temperature over the past 1,000 years is under development and is scheduled for completion and on-line availability in late FY 2004. Such maps, data, and manuscript references will provide spatially-detailed information about Arctic temperature trends over the last millennium, which can be used to compare more recent changes with the patterns of change from the mid-Holocene geologic epoch...
Researchers supported by NSF, along with researchers at NASA and USGS, have begun a multi-year data analysis and climate modeling effort to create 3-dimensional global data sets of middle Pliocene epoch (~ 3.0 million years ago) ocean temperature and salinity. This will create the most comprehensive global reconstruction for any warm period of Earth's climate prior to the most recent past. Estimates of middle Pliocene global warming suggest that temperatures were approximately 2°C greater than today. This level of warming is within the range of projected global temperature increase in the 21 st century. No other time period in the past 3 million years approaches this level of warming. Analysis of this period challenges the science community's understanding of the sensitivity of key components of the climate system and how the system is simulated, i.e., polar vs. tropical sensitivity, the role of ocean circulation in a warming climate, the hydrological impact of altered storm tracks, and the regional climate impacts of modified atmospheric and oceanic energy transport systems.
The report states:
Multiple ensemble simulations of the 20th century climate have been conducted using climate models that include new and improved estimates of natural and anthropogenic forcing. The simulations show that observed globally averaged surface air temperatures can be replicated only when both anthropogenic forcings, e.g., greenhouse gases, as well as natural forcings such as solar variability and volcanic eruptions are included in the model.
<img src="http://www.usgcrp.gov/usgcrp/images/ocp2004/images/OCP04-05_fig9.jpg">
I believe this conclusion is reasonable. At this time, it is still unclear as to what share of the climate change is attributable to natural factors and what share is attributable to human ones. This report notes that both are involved but does not attempt to blame one or the other type of factor for most of the warming that has occurred. It does acknowledge that most of the pre-1950 warming was due to natural factors.
I will note that the PCM model which was employed to generate the above graph still leaves much to be desired. It deals with only a select number of natural forcings (volcanic and solar) but does not appear to incorporate additional cyclical variables such as ENSO, PDO, etc., if the key at the bottom of the chart is to be taken at face value.
As a very quick illustration of the importance of ENSO data, among others, for assessing climate change the following are two graphs:
<img src="http://www5.wright-weather.com/bb/attachment.php?s=&postid=300445">
1) The top graph illustrates the global mean temperature since just after 1880.
2) The bottom graph illustrates the 30-year moving average of the anomaly in ENSO Region 3.
In general, it appears that when the 30-year anomaly is "warm", the global temperature tends to be in a cycle where it tends to decline. When the 30-year anomaly in this region is "cool," the opposite is true.
There also appears to be a short lag between the 30-year anomaly and response in the global temperatures.
Notice that from around 1970 to the late 1990s, there was an especially pronounced "cool" period in the 30-year anomaly for Region 3. During this time, the global temperature rose especially sharply.
Now, a few years after the 30-year ENSO 3 anomaly has begun to move into "warm" territory, the global temperature may be showing indications of cooling.
Needless to say, this information does not argue against any impact from a buildup of CO2 in the atmosphere. Rather, it argues that incorporation of ENSO data, not just from Region 3, could add significant value in understanding global climatic trends.
On the matter of ENSO data, the report states:
A new multi-year assimilation of in-situ and satellite data into an ocean model highlighted the importance of the interior ocean mechanisms (as compared to boundary currents such as the Gulf Stream) on timescales of weeks to months. Investigators found these mechanisms in the interior ocean play a critical role in altering the water mass exchanges between the midlatitude eastern Pacific Ocean and the the tropical Pacific where El Niño develops, suggesting that remote effects on El Niño should be more carefully considered by prediction models. Further, these relatively fast mechanisms were found to govern more generally the transports and exchanges between the tropical and midlatitude ocean and thus could be an important factors for observing and modeling the longer-term changes (e.g., interannual to decadal variability) of the Pacific Ocean.
Unlike the two previous reports on which I commented--the California projections and the European ones--this report signals that important research that I would like to see (paleoclimatic) is underway.
It declares:
Based on a new synthesis of data from the Holocene Thermal Maximum (~9,000 years ago), warming is asynchronous and asymmetric across the North America Arctic region. Warming begins in the west and sweeps eastward. A georeferenced database of annually resolved records of Arctic temperature over the past 1,000 years is under development and is scheduled for completion and on-line availability in late FY 2004. Such maps, data, and manuscript references will provide spatially-detailed information about Arctic temperature trends over the last millennium, which can be used to compare more recent changes with the patterns of change from the mid-Holocene geologic epoch...
Researchers supported by NSF, along with researchers at NASA and USGS, have begun a multi-year data analysis and climate modeling effort to create 3-dimensional global data sets of middle Pliocene epoch (~ 3.0 million years ago) ocean temperature and salinity. This will create the most comprehensive global reconstruction for any warm period of Earth's climate prior to the most recent past. Estimates of middle Pliocene global warming suggest that temperatures were approximately 2°C greater than today. This level of warming is within the range of projected global temperature increase in the 21 st century. No other time period in the past 3 million years approaches this level of warming. Analysis of this period challenges the science community's understanding of the sensitivity of key components of the climate system and how the system is simulated, i.e., polar vs. tropical sensitivity, the role of ocean circulation in a warming climate, the hydrological impact of altered storm tracks, and the regional climate impacts of modified atmospheric and oceanic energy transport systems.