You have two options:

• Reproject to an Equal Area coordinate system that's relevant for your area-of-interest and then the regular AreaCalculator
• Use the GeographicAreaCalculator custom transformer, it will reproject to a generic Equal Area system centered on your feature and then calculate the area. Because of that there might be small variations between this option and the first one.

@Hans van der Maarel​ , we are doing area calculations for global datasets. I tried a couple of Equal Area projections, do not seem to work well on global datasets as expected. Will try this GeographicAreaCalculator and see how it compares with the arcgis geodesic area calculations. The latter has been accepted by our users.

@Hans van der Maarel​ Just let you know the GeographicAreaCalculator custom transformer gives exactly the same results as using this in ArcGIS -  http://dmahr.com/2015/07/geodesic-areas-arcmap-field-calculator/