Climate and Global Dynamics Division

Maurice L. Blackmon, Director

Director’s Message

Most of the work in the Climate and Global Dynamics Division (CGD) involves analysis of either observations or model-generated data or the development and use of models.  Climate science is now trying to deal with uncertainties due to biases or inadequacies in most, if not all, of these activities.

 

Our climate data sets do not extend far enough back into the past.  Some data sets are plagued by inhomogeneities due to changing data source inputs over the time of their collection.  Other data sets that allegedly measure the same quantities show differences due to instrumental biases or inadequate analysis techniques.

 

Climate models contain representations of processes that are inadequate in some way.  This leads to model simulations that do not adequately reproduce observations in some important aspects.

 

What are the consequences of these uncertainties?  Some of the most important questions that we are trying to answer either go without answer or go without a convincing answer.

 

For example, there has been considerable controversy during the past few years over whether the climate is warming or not.  The data sets being used to examine this question have all the problems mentioned above and more.  In particular, the temperature record based on standard techniques, that is, thermometers, shows warming, but a satellite data set has not.  Difficult, painstaking work, much of it done in CGD, has resolved this discrepancy, and now it is becoming clear that the answer is “yes,” the climate is warming.

 

A different uncertainty concerns the magnitude of climate change over the next century and beyond.  Climate models developed around the world have been used to simulate the climate change of the 21^st century using a commonly assumed set of changes in greenhouse gases and other forcing factors.  The result from this activity is large uncertainty, with the different model projections showing warming at the end of the 21^st century varying by up to 4.5°C (or about 8°F).

 

If this were a strictly scientific disagreement, we would handle this uncertainty through the usual process of comparison and debate.  However, there are political and economic implications, as well.  If the higher values of climate change are correct, we might need to take major steps to reduce greenhouse gas emissions to reduce climate change.  If the lower model estimates are more correct, we might have more time to make decisions on what to do. 

 

It seems to me that the present uncertainty is so large, and the economic implications so large, that a political decision will be difficult to achieve in the near future.  In order to serve the national need, and indeed the world’s need, our research must be increasingly focused on reducing the uncertainty of our model projections.  This will not be easy, and it will take time.  However, I expect that work being done at NCAR and within CGD will be important in allowing us to provide our leaders with better information that is necessary for wise decision-making.