A review of four decades of atmospheric trace gas measurements at Cape Point, South Africa

Abstract

South Africa’s Cape Point (CPT) trace gas observatory, operated by the South African Weather Service (SAWS), has been monitoring mole fractions (mol/vol) of ambient greenhouse gases (GHGs), e.g. carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and selected halocarbons (CFCs and CCl₄) since the late 1970s. In addition, the Cape Point trace gas observatory boasts the longest atmospheric carbon monoxide (CO) dataset continuously from 1977 in the Southern Hemisphere (SH). Instruments for the measurement of radiation and other selected gases, such as ozone (O₃), have gradually been added since the inception of measurements. The year 1995 heralded a milestone when the Cape Point observatory became part of the World Meteorological Organization’s (WMO) Global Atmosphere Watch (GAW) programme. Besides supplying data to the World Data Centres, it also supports the local database, South African Air Quality Information System (SAAQIS). These affiliations, which require strict measurement protocols, make the Cape Point data records available within the global data centres. Due to Cape Point’s location in a mostly pristine marine environment and its proximity to the Southern Ocean, measurements are highly valued in the United Nations Environment Programme (UNEP)/WMO Ozone and IPCC Climate Assessments and serve as a bellwether for regional changes in southern African atmospheric composition. A review of selected climate change relevant trace gas measurements acquired at Cape Point is presented here.

ACKNOWLEDGEMENTS

The authors would like to thank the South African Council for Scientific and Industrial Research for the early contribution they provided; Department of Environmental Affairs for supplying core funding for Cape Point to ensure continuous operation; the late H.E. Scheel, Karlsruhe Institute of Technology, for his continued support and advice.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

List of Abbreviations and Acronyms

ANSTO	=	Australian Nuclear Science and Technology Organisation
CPT	=	Cape Point
CRDS	=	Cavity Ring Down Spectroscopy
CSIR	=	Council for Scientific and Industrial Research
ECD	=	Electron Capture Detector
EMPA	=	Swiss Federal Laboratories for Material Science
ENSO	=	El Niño Southern Oscillation
ESRL	=	GMD Earth System Research Laboratory Global Monitoring Division (of NOAA)
FID	=	Flame Ionization Detector
GAW	=	Global Atmosphere Watch
GAWSIS	=	Global Atmosphere Watch Station Information System
GC	=	Gas Chromatograph
GHGs	=	Greenhouse Gases
ICP	=	InterComParison
IMK-IFU	=	Institute of Meteorology and Climate Research-Atmospheric Environmental Research (part of KIT)
IPCC	=	Intergovernmental Panel on Climate Change
KIT	=	Karlsruhe Institute of Technology
NDIR	=	Non-dispersive infrared
NOAA	=	National Oceanic and Atmospheric Administration
SAWS	=	South African Weather Service
UNFCCC	=	United Nations Framework Convention for Climate Change
UV	=	Ultraviolet
WDCGG	=	World Data Centre for Greenhouse Gases
WMO	=	World Meteorological Organization

Additional information

Funding

BK would like to thank the University of the Western Cape for the Prestigious Postdoctoral Bursary and the University of Bristol for collaborative and financial support.