def custom_scatterplot(ax, x, y, error, xlims, ylims, color='green', markerscale=100):
    """Customized scatter plot where marker size is proportional to error measure."""
    
    markersize = error * markerscale
    
    ax.scatter(x, y, color=color, marker='o', s=markersize, alpha=0.5)
    
    ax.set_xlim(xlims)
    ax.set_ylim(ylims)
    
    return ax