The term “cryosphere” refers to the frozen water regions on the Earth: e.g., glaciers, snowcovered regions, sea ice and permafrost regions. Glaciologists define an “ice age” for the Earth as periods where permanent ice sheets are present in both hemispheres. Therefore, technically, since there are permanent ice sheets in Greenland and Antarctica, we are currently in an ice age. However, fortunately, we are in an “interglacial” period of this ice age – much milder than the glacial period that ended 10-15,000 years ago.
Many people rely on the UN’s Intergovernmental Panel on Climate Change (IPCC)’s Assessment Reports for evaluating trends in the cryosphere. These IPCC reports tend to describe quite accurately all those trends related to the cryosphere that imply “the ice is melting dramatically” (IPCC, 2014; 2019). However, they tend to downplay or overlook those trends which contradict this narrative. If we are interested in studying climate change, it is important to consider all the relevant trends – not simply the ones that agree with our chosen narrative. Therefore, in this talk (and accompanying abstract), I will briefly summarize the current scientific understanding of what we know about cryosphere trends and highlight some of the key observations that have been overlooked or downplayed by recent IPCC reports.
In the talk, I summarize the key trends associated with each aspect of the cryosphere (glaciers, ice sheets/ice shelves, sea ice, permafrost, and snow cover) and compare these trends to those described by the IPCC reports and the “hindcasted” trends that the global climate models (GCMs) used for the IPCC reports argue should have occurred. There, I demonstrate that the GCM hindcasts fail to replicate many of the observed trends, and that the IPCC reports are remarkably selective in which trends they report on. However, for brevity, in this extended abstract, I will mostly focus on the trends themselves.