Which three paragraphs in this excerpt from the article "the melting arctic" from the european environmental agency rely on expert opinion to support the organization's point of view?
greenland's ice sheet contains enough water to increase global sea levels by 7 meters. in any case, if it were to melt completely, it would take many centuries. recent melting of the greenland ice sheet is estimated to have contributed up to 0.7 millimeters a year to sea level rise (about one quarter of the total global average sea level rise of about 3.1 mm/year). projections for global average sea level rise estimates by 2100 vary from 0.2 to 2.0, depending on the model and scenario used.

"there is substantial uncertainty around by how much the sea levels may actually increase," said professor david vaughan from the british antarctic survey during his presentation. "once sea level rises, it is quite difficult to make it fall again. at the moment, the sea level is increasing by about 3 mm per year, but with climate change, this rate is very likely to increase."

vaughan continued, "there are different factors behind sea level rise. about one third of the rise we can expect could be linked to the thermal expansion of oceans. melting mountain glaciers are also predictable and their contribution can be estimated roughly. the big uncertainty is linked to ice sheets in greenland and the antarctica. we have studies on how they are losing ice, but projections come with high levels of uncertainty."

warmer temperatures in the arctic accelerate the melting, which result in darker surfaces on the sea and land. these darker surfaces retain a larger part of the solar energy instead of reflecting it back. warmer air and water temperatures in the region also affect the surrounding land, including the permafrost, which has started melting both on land and at sub-sea level. .

in addition to potentially causing sea levels to rise and contributing to global warming, the arctic melting could also alter the oceans' salinity levels and affect ocean currents. moreover, increased absorption of co2 in the oceans can lead to ocean acidification and this can in turn alter the composition and distribution of key arctic species like crustaceans, krill and plankton.

according to morten olsen, chair of a recent arctic council assessment on changes in arctic snow- and ice-conditions, "changes in the climate and cryosphere risk fundamentally altering the arctic ecosystems. warmer water temperatures might result in invasive species moving north, which would affect local species and ultimately local economies."