There was nothing profound that led me to my current career.
Although I am a climate scientist with primary training in atmospheric
sciences, neither weather nor climate were passions of mine as a
youth. However, I was fortunate to be adept in mathematics, and my
undergraduate work led me to a First Class honours degree in
Mathematics at the University of Canterbury in New Zealand, where I
was raised. In seeking employment, I was attracted to meteorology
primarily through the link with fluid dynamics, which I had studied
earlier. A key advantage of employment in the New Zealand
Meteorological Service at that time was training in diverse aspects of
meteorology as a prelude to
working as a junior weather forecaster
(shift work!). This was prior to my winning a New Zealand Research
Fellowship to study overseas (at the Massachusetts Institute of
Technology), where I was able to further diversify my background with
theory and modeling. Following my doctorate, I returned to New Zealand
for nearly seven years before moving to United States; a consequence
in part of having married an American girl.
A great deal of my research has focused on regimes, or persistent
patterns of variability, in weather and climate. This interest stemmed
from the early part of my career in New Zealand, where I observed as a
forecaster what appeared to be weather patterns that lasted for more
than a season. Subsequently these patterns have been linked in part to
the El Niño phenomenon, partially through my own work. The cited work
was an attempt to provide as comprehensive analysis of the
observational record as possible on time scales from days to
multi-decadal, with a focus on North Pacific variability and links to
El Niño. This work therefore enabled the documentation of how storm
tracks change as the atmospheric circulation changes in this region,
and it identified multi-decadal climate variations that are of
considerable importance and which may well be linked to climate
change, and specifically to global warming. It further identified the
effects of these variations on rainfall, temperatures, the ocean, and
such things as the salmon harvest.
Our recent work has raised questions about how El Niño will change
as climate changes, and detailed statistical and diagnostic analysis
has provided a good basis for believing that there is a relationship.
We have also documented more comprehensively how El Niño itself
evolves in various manifestations (wind, temperature, atmospheric
circulation, cloud, radiation, precipitation, storminess, movement of
heat and energy, exchanges of heat and moisture with the surface)
throughout its life cycle, and how that evolution appeared to change
abruptly around about 1976-77, as was first partly outlined in the
cited article. This has subsequently become well recognized as the
1976-77 climate shift. We have also recently documented El Niño
relationships to global mean temperature and how it is manifested
through the local surface temperatures all over the globe.
How El Niño changes as climate changes and global warming
progresses is a critical question of great importance for many regions
of the globe. While our exploratory analyses are suggestive and form
useful hypotheses for future work, climate models do not yet simulate
El Niño well enough and are too different from each other to have any
confidence in their projections. This itself is an indication of a
lack of adequate understanding of some aspects of El Niño and its
role in the global climate system. Accordingly, we continue to seek
improved analyses of the past and associated diagnostic studies that
will clarify the role of El Niño and improve its prediction. A focus
for some of the research is quantitative diagnostic estimates of the
energetics of El Niño, so that we can track how the heat builds up in
the ocean and is subsequently redistributed and dissipated during the
El Niño event. The underlying hypothesis is that El Niño exists and
plays a role in the Pacific Ocean as a means of removing heat from the
equatorial regions of the ocean, where it would otherwise build up. An
implication of this, if correct, is that further heat buildup from
increasing greenhouse gases in the atmosphere would lead to increased
magnitudes and/or frequency of El Niño events. Nevertheless, we do
not expect this to be simple, and nature always seems to be able to
come up with surprises as to just what the future holds.
Dr. Kevin E. Trenberth
National Center for Atmospheric Research
Climate Analysis Section
Boulder, Colorado, USA
n this essay, Dr. Kevin Trenberth talks about his highly cited
work in global warming. Our Special Topics analysis of global warming
research over the past decade ranks Dr. Trenberth among the top 10
most-cited scientists in this particular area. His most-cited paper is
also the #1 paper in the global warming analysis: "Decadal
atmosphere-ocean variations in the Pacific," (Climate
Dynamics 9 [6]: 303-19, March 1994). This paper had 343 citations
at the time of the analysis, and currently has 365 citations in the 
Web product. Dr.
Trenberth’s work can be found in the main database in the
Geosciences field. Dr. Trenberth is a Senior Atmospheric Scientist and
Head of the Climate Analysis Section of the National Center for
Atmospheric Research in Boulder, Colorado.