Around the time I finished high school, the ozone hole was discovered, forests were dying from acid rain, and the Chernobyl disaster sent radioactive fallout and psychological shock waves throughout Europe.
I did not fully understand any of these problems but realised that human development was on a collision course with nature, and I needed to get an education to learn more.
I enrolled as a student of physics at Marburg University in Germany where I was living. Three decades later I am a climate scientist in New Zealand, working on global climate change – the most pressing of all collision courses between humans and nature.
Here, the Southern Hemisphere offers some particularly interesting and scientifically challenging problems to climate scientists like me.
In 1896, Swedish physicist Svante Arrhenius first hypothesised that carbon dioxide (CO2) released by burning coal was going to warm our climate, and even calculated how much warming he expected for a doubling of the amount of CO2 in the atmosphere.
More than a century later his estimate is still valid, but we now understand much better why quantifying this “climate sensitivity” is so difficult.
Also read | Interview | ‘We’re Finally Talking About Solutions on the Scale of the Crisis We Face’: Naomi Klein
The leading complication is the response of clouds to warming (Arrhenius left these out of his calculation).
As seen from space, clouds make our planet a lot brighter or more reflective to incoming sunlight than it would be in their absence. Both their abundance and brightness greatly influence the amount of heat in the climate system.
To assess the links between clouds and climate change, nowadays scientists use global climate models. These are large computer formulations of the laws of physics that govern the climate system.
Over the Southern Ocean most such modern climate models routinely fail to correctly simulate these ubiquitous clouds, allowing too much sunlight to reach the ocean surface. Consequences of this problem in simulations often include too warm a sea surface, underestimated sea ice cover, and misplacements in the mid-latitude storm track that sends familiar low-pressure weather systems to New Zealand.
There are two roots to this problem: One is that clouds are usually a lot smaller than the 150km or so of spatial resolution that is typical of modern climate models. The other is that their brightness, and sometimes their very existence, are influenced by a variety of “aerosols”, i.e. microscopic particles and droplets composed of materials such as sea salt, sulphuric acid, organic matter, or mineral dust. In particular, in sub-zero temperatures it requires the presence of certain aerosols to cause cloud droplets to freeze. In their absence clouds can remain liquid even in temperatures down to about -40 degrees Celsius.
Whether a cloud is liquid or frozen makes a big difference to that cloud’s brightness and the amount of water the cloud will hold. Little is known about the make-up, abundance, and geographic distribution of such “ice nucleating particles” in the Southern Ocean region, and many climate models therefore do not represent such particles at all.
Also read | Karnataka’s Cloud-Seeding Plan Needs More Science, Less Politics
This means that formulations of cloud freezing used in climate models, which are based on data collected under relatively polluted Northern-Hemisphere conditions, do not adequately describe this process down here. This explains why models simulate ice clouds that really, in the Southern-Ocean region, should be liquid.
The problem is one of a few specific Southern Hemisphere climate issues that my colleagues and I have been investigating. By international standards we are a very small group, and our efforts to model the Earth’s climate rely heavily on collaboration with overseas partners. By picking our battles smartly, and adopting a Kiwi can-do attitude, we are striving to contribute what we can to furthering the science of global climate change.
We may have our heads in the clouds but our goal is that our research contributes to more reliable climate simulations for New Zealand, informing climate policy and adaptation.
Olaf Morgenstern is an atmospheric scientist with Niwa.
This story originally appeared in Stuff. It is republished here as part of The Wire‘s partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.