Gasparini, Blaz, Dr.

Dr.  Blaz Gasparini

CHN  P 15.1 

Universitätstrasse 16

8092 Zürich


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Additional information

Research area

PostDoc in the modeling part of the group of Prof. Ulrike Lohmann
You normally find me in office P15.1.

Research interests

  • climate modeling
  • cirrus cloud seeding and geoengineering in general
  • cloud feedbacks
  • climate dynamics


Supervision of Master and Bachelor projects

    • Simon Förster: Sensitivity of ECHAM6-HAM2 to sedimentational description (Msc project)


    • Anne-Sophie Scheidegger: The Impact of Large Volcanic Eruptions on Climate (Msc project)


    • Tim Schär: Cirrus cloud seeding with ECHAM-HAM (Bsc project)


    • Monika Feldmann: Cirrus seeding and stratospheric sulphur injections in the Arctic (Bsc project)


  • Laure Poncet: What is the limit of cirrus cloud seeding? (Bsc project)

Teaching assistant

Curriculum Vitae

2007-2010        BSc in Physics, University of Trieste (Italy)

2011-2013        MSc in Atmospheric and Climate Science, ETH Zürich

2013 - 2016      PhD student at ETH Zürich

Nov 2016 -        PostDoc at ETH Zürich

Additional information


Gasparini and Lohmann (2016):

Why cirrus seeding cannot substantially cool the climate, JGR


Its essence in short:

Can cirrus cloud seeding help to "save" the climate?

Can cirrus cloud seeding help cool the climate?


Gasparini et al. (2016):

Is increasing ice crystal sedimentation velocity in geoengineering simulations a good proxy for cirrus cloud seeding?, ACPD




Figure 1: Not seeded cirrus cloud (left) formed by homogeneous nucleation of soluble aerosols contains a large number of small ice crystals, unlike the one formed in presence of solid aerosols (e.g. dust) or seeded particles. The homogeneous cloud is thicker in shortwave (SW) and less transparent for longwave (LW) radiation compared with a seeded, heterogeneously formed cloud. Its larger ice crystals additionally imply a shorter cloud lifetime. The basic idea of cirrus seeding is to transform cirrus clouds that look like the one on the left to those that look similar to the one on the right, implying a negative radiative anomaly and cooling.


Figure 2: Cirrus cloud types typical altitude range and formation mechanism as simulated by ECHAM6-HAM2 model. 

Fig2: Impacts of volcanic eruptions on climate [Robock, 2000]

What is geoengineering?

To start with, you can read my blog post on stratospheric sulphur injections published in ETH Zukunftsblog.


Figure 3: A schematic of various geoengineering ideas. Highlighted the two on which I am doing some modelling based research.

Geoengineering (GE, equivalently known as climate engineering) proposals aim at a reduction of global temperatures, that would counteract the anthropogenic warming and stabilise the Earth's energy budget and climate. The proposed methods are diverse and vary greatly in terms of their technological characteristics and possible consequences. GE strategies can be divided into two groups [Royal Society, 2009]:


  • -Solar radiation management (SRM) schemes that modify the radiation balance by reflecting part of the incoming solar radiation back to space. Yet, SRM techniques cannot counteract all negative effects of increasing CO2 concentration, e.g. ocean acidification.
  • -Carbon dioxide removal (CDR) methods that remove CO2 from the atmosphere, directly reducing greenhouse gas forcing.


One of the most discussed SRM techniques are the so called stratospheric sulphur injections, artificially building up the stratospheric aerosol layer. The stratospheric aerosols have often considerable impacts on both the atmospheric chemistry and surface radiative balance [Robock, 2000] and thus need to be carefully simulated in global climate models that are able to simulate relevant microphysical processes. These impacts might be negligible or small in the volcanically quiescent periods, but can significantly alter the surface temperature after explosive volcanic eruptions or in the case of artificial aerosol emissions.

Geoengineering - a (temporary) solution of the climate problems or only "geopiracy"?

Even if geoengineering might be able to couteract the rising global temperature due to the greenhouse gas effect, it still leaves many unanswered questions, summarised in 20 reasons why geoengineering may be a bad idea [Robock, 2008].

When thinking about geoengineering in a broader context, I personally agree with the general conclusions of McCusker et al. 2012 that briefly summarizes the risks associated with geoengineering as:
"The question remains as to whether the apparent global warming abatement geoengineering may provide outweighs the


  • -risk of foreseen consequences being worse than predicted,
  • -risk of altogether unforeseen negative consequences,
  • -risk of failure in international cooperation,
  • -risk of failure of the chosen geoengineering mechanisms, leading to rapid temperature rise, and
  • -risk of choosing winners and losers in the climate battle.''


If I assume that the scientific, technical and financial questions regarding the implementation of stratospheric injections could be solved, we still face a lot of considerations a future society would need to take into account, following closely the ideas of Robock 2012b:


  • -Who would be in control of a world thermostat?
  • -Who can define when the benefits of implementation of such schemes would outweigh the potential downsides? Can we allow/is it ethical to implement CE at all, if there are some negative effects, despite them being regionally limited?
  • -Who will be responsible for the delivery and maintenance of the stratospheric aerosol cloud? Would we allow a multinational company to be in charge of it? Or a foreign military?
  • -Who will be in charge of the political platform unifying all the world's countries in an efficient and flexible organ? Will it be the weak and inefficient UN?


Finally, is geoengineering research ethical at all? I was dealing with this question before the start of this project and I will probably have to think about it even more often in the future. To briefly answer it, I again make use of Robock's thoughts: Indoor geoengineering research is ethical to provide information to policymakers and society so that we can make informed decisions in the future to deal with climate change [Robock, 2012a].
To sum it up, curiosity-driven indoor geoengineering research is useful even if we might never need/want to take advantage of it.


What is sustainable development?

Under this link you find one of the publications for youth and broader public we prepared during the time I was involved in the youth association No Excuse Slovenia.

What is sustainable development?

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Mon Jun 26 16:10:16 CEST 2017
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